Blocks have gotten a whole lot of core functionality in Drupal 8.  The new interface can trip you up as you get used to the changes, especially when you start adding Views blocks into the mix.

Drupal 8 Block Overview 

Drupal 8 blocks are managed from the same location as in Drupal 7, Admin > Structure > Block, but the new menu, with tabs for Block Layout and Custom Block Library, is your first hint that something has changed under the hood.

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