Form Types can be represented with a tree. Some types inherits each other and all form types inherits the field type (as of Symfony 2.0, form in 2.1).

We currently have a Inherit options section in each reference article with some relevant inherit options. In order to keep this up to date, someone needs to:

• Recheck every parent/child relation (is it correct? is there a link?)
• Recheck the inherit options. Are they relevant? Are their other relevant
  options that should get placed here?
• Add a list of links to the description of some options which are not
  relevant enough to get documented on this page. This to avoid long
  articles.

A 'tree' of all parent/child relations (in 2.0) and their options can be found in this gist.