Content type / block or page .. how do we create a small text for a page in D8
Blocks can be used for many things including showing simple texts. Go to /block/add and create a block. Here you can provide a description and some body text. After saving your block you are redirected to the block configuration where you can place it.

By placing the block Drupal creates a block instance. For more information please see: https://www.drupal.org/docs/8/core/modules/block/overview