The 2col template in twig

layout-2col.html.twig

{#
/**
 * @file
 * Template for a 2 column layout.
 *
 * This template provides a two column display layout, with each column
 * roughly equal in width.
 *
 * Variables:
 * - attributes: Attributes to use for the layout like additional classes and id.
 * - content: An array of content, each item in the array is keyed to one
 *   region of the layout. This layout supports the following sections:
 *   - content.left: Content in the left column.
 *   - content.right: Content in the right column.
 */
#}
<div class="layout-display layout-2col clearfix {{- attributes.class }}" {{- attributes }}>
  <div class="layout-region layout-col-first">
    <div class="inside">{{ content.left }}</div>
  </div>

  <div class="layout-region layout-col-last">
    <div class="inside">{{ content.right }}</div>
  </div>
</div>