As Lazarus is a "community" project, creating the "Help" also needs help. Have a look at
this page and
this one to see what is done, how it can be done and how you can help. Feel free to participate and share your work with the community.
A lot of information you can get by looking at the sources. Using <ctrl> <mouseclick> on a function / procedure / class will bring you to the place in the sources where it is declared. For a few examples look at the
Lazarus Documentation and follow the links to the available explanations. Some of these articles come with samples.