HTML block is a long block of static text. It is used as a component that can be inserted into page layout position. 

To create a HTML block

Go to "Contents" -- "HTMLBlocks"

Click "New" to create a new HTML block. 

HTML block has two fields, a name and a body with richtext editor. 

HTML block supports multilingual, for more information, refer to the Multilingual charpter. 

To use HTML block on page, in the page design screen.

Click the "+" icon under page position, select "HTMLBlock". 

In the opened window, select the right block for the position.