Review how blocks in Drupal 8 are fieldable and can be placed in multiple different regions instead of only one region.
Blocks are individual pieces of your site’s web page layout. They are placed inside the regions (see Section 2.1, “Concept: Regions in a Theme”) of your theme, and can be created, removed, and rearranged in the Block layout (admin/structure/block) administration page. Examples of blocks include the Who’s online listing, the main navigation menu, and the breadcrumb trail. The main page content is also a block. From: https://www.drupal.org/docs/user_guide/en/blocks-chapter.html
Paths to block layout and regions: Navigate to admin/structure/block
Blocks are fieldable entities in Drupal 8, similar to beans in Drupal 7. To make a new custom fieldable block navigate to /block/add?destination=/admin/structure/block/block-content