"Blocks" are a core feature of Drupal. If you are going to work on a Drupal website, you are going to work with Blocks. "Super Blocks" offer tons of style and layout options. Also, you can easily COPY Super Blocks, which saves you a ton of work!
This is a special kind of Block which acts as a side menu. It can be added to any page. The Menu Block on the Add and Edit Content page is an example of one.
"Mercury Blocks" are containers for News or Events feeds. The "Upcoming Events" and "News" Blocks on the homepage are examples.