Title blocks define the size and appearance of a drawing sheet.
Think of title blocks as templates for the drawing sheet. You create a title block family using the Family Editor. For each title block, you specify the sheet size and add borders, a company logo, and other information. You save the title block family as a separate file with an RFA extension.
Typically, you create custom title blocks and save them in the following location: %ALLUSERSPROFILE%\Autodesk\RVT 2021\Libraries\<language and locale>\Titleblocks. You then add these title blocks to a default project template, so they automatically load when you create a project.
If the custom title blocks are not included in the project template, you can load title blocks into a project.