The video course that I took to get started in Drupal did a wonderful job of showing me how to create a custom block and put it in an area on my webpage. Unfortunately, I have since found that except in rare instances it's the wrong thing to do.
The "right" way, at least as far as I am concerned is to create a content type and then create a view as a block. Then place the block where you would have placed the custom block.
Doing it this way allows anyone with permission to edit that content to edit the content of the "custom" block.
Of course if it's a block you don't want anyone messing with, you should create a custom block and not give anyone permission to edit custom blocks.