When you add blocks on a page, they have static content. What you add in the block is what you will see on site. Dynamic blocks allow you to use dynamic data which is different for different pages. For example, a dynamic title allows one to get the title of a post and show it in global templates.
All our sites and even this documentation page use dynamic blocks (breadcrumb, dynamic title, categorization, and page navigation, etc).
Dynamic fields require to have our Query addon. Query addon can be purchased as a separate addon, as part of the Design/Seo plan, and as part of the All in One plan
Here is a set of all blocks of Query addon. Click on each block and find more details about each of them