Blocks library allows you to simply add already created blocks to your document so you can build them even quicker! The advantage is that if you decide to make changes to a block, these changes will be automatically applied to all the templates where the block exists, removing the need to spend time making these changes one template at a time.
The blocks are stored in the Library section that can be found in the menu on the left of the homepage. Blocks are good to use for data that is often repeated or unchanged. You can add as many new blocks as you want in the library or edit already existing ones.