Loading jQuery via a Google Hosted Libraries allows it to load quicker, as other sites who have included it from Google's Hosted Libraries will ensure that jQuery is already available in the cache of many of your visitors' computers.
The following snippet of code will attempt to load jQuery from Google Hosted Libraries and fall back to a local version if it did not load correctly for any reason. Ensure that you update the path to your local version of jQuery in the code below.
<!-- Load jQuery via Google CDN, fall back to local version if not loaded -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script>window.jQuery || document.write(unescape('%3Cscript src="/path/to/js/jquery.min.js" type="text/javascript"%3E%3C/script%3E'));</script>