Sitecore Content Search Analyzers

Sitecore.ContentSearch.Lucene.DefaultIndexConfiguration.config

<analyzer type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzer, Sitecore.ContentSearch.LuceneProvider">
  <param desc="defaultAnalyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
    <param desc="defaultAnalyzer" type="Lucene.Net.Analysis.Standard.StandardAnalyzer, Lucene.Net">
      <!-- To run a different version of Lucene, change the version.
                     Usage: If a problem is found in the latest version to Lucene and a previous version is more stable, you can change the version
                            attribute and run in the version that is stable e.g. Lucene_29 or Lucene_23.
                -->
      <param hint="version">Lucene_30</param>
    </param>
  </param>
  <param desc="map" type="System.Collections.Generic.List`1[[Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider]]">
    <map hint="list:Add">
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">ja-JP</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Lucene.Net.Analysis.CJK.CJKAnalyzer, Lucene.Net.Contrib.Analyzers">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">ar-AE</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Lucene.Net.Analysis.AR.ArabicAnalyzer, Lucene.Net.Contrib.Analyzers">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">pt-BR</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.Contrib.BrazilianAnalyzer, Sitecore.ContentSearch.LuceneProvider">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">cs-CZ</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Lucene.Net.Analysis.Cz.CzechAnalyzer, Lucene.Net.Contrib.Analyzers">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">de-DE</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Lucene.Net.Analysis.De.GermanAnalyzer, Lucene.Net.Contrib.Analyzers">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">el-GR</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Lucene.Net.Analysis.El.GreekAnalyzer, Lucene.Net.Contrib.Analyzers">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">fa-IR</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.Contrib.PersianAnalyzer, Sitecore.ContentSearch.LuceneProvider">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">fr-FR</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.Contrib.FrenchAnalyzer, Sitecore.ContentSearch.LuceneProvider">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">nl-NL</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.Contrib.DutchAnalyzer, Sitecore.ContentSearch.LuceneProvider">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">ru-RU</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Lucene.Net.Analysis.Ru.RussianAnalyzer, Lucene.Net.Contrib.Analyzers">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
      <mapEntry type="Sitecore.ContentSearch.LuceneProvider.Analyzers.PerExecutionContextAnalyzerMapEntry, Sitecore.ContentSearch.LuceneProvider">
        <param hint="executionContext" type="Sitecore.ContentSearch.CultureExecutionContext, Sitecore.ContentSearch">
          <param hint="cultureInfo" type="System.Globalization.CultureInfo, mscorlib">
            <param hint="name">th-TH</param>
          </param>
        </param>
        <param desc="analyzer" type="Sitecore.ContentSearch.LuceneProvider.Analyzers.DefaultPerFieldAnalyzer, Sitecore.ContentSearch.LuceneProvider">
          <param desc="defaultAnalyzer" type="Lucene.Net.Analysis.Th.ThaiAnalyzer, Lucene.Net.Contrib.Analyzers">
            <param hint="version">Lucene_30</param>
          </param>
        </param>
      </mapEntry>
    </map>
  </param>
</analyzer>

What is the purpose of this configuration?