Content blocks, or just Blocks, are additional editable areas of your page, configured by your designer in the layout files.
A block can be set up so that they either show the same content across all pages that share that block, or to show unique content specific to each page of the site. It's up to the designer to set that up.
Block's each have a unique ID that refers to that specific editable area. Once a block is set up, you'll likely never need to change this value.
When a content block is first set up, it will be blank, so an Add Block icon will appear in its place, like this:
Click that to create the new content block. Each block has a title and body, and a few special options.
Once you've created the block, whenever you're logged in as an admin you'll always see edit buttons like the following at the top of the block:
You may see blocks with an Add button still present. This means that this content area was set up so that, like normal, pages can share the content of your block, but in this case you can "override" the content for individual pages as well.
An example where this is useful would be a main sidebar block for your overall website, with the ability to add custom sidebar content on a per-page basis that should appear instead of the default content.
Blocks have a couple extra options available that let you choose whether to display its title or not, and whether the block is visible to the public, members-only, or private (admin only).
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