I've been asking the same question to myself, and i spend quite a while searching for the answer on the web. But i've finally succeeded you just have to type this in terminal.app :
man tcsh
This is because tcsh (TC shell) is the shell that's terminal is using.
Now you just <optionnal>hit space until all is displayed, select it all, choose 'Save the selected text as' in the 'File' menu, then open it using 'Textedit' and then</optional> search for chapter 'Reference' (about the middle) where all the builtin commands are described.