Perhaps the who and users commands are available to you.

The FAQ section has a crib sheet, it's not specific to MacOS but probably a good start. Unix Basic Command

Once you know a few commands, Googling for pages which contain many of them will help you find more of the same. macos cat ls mkdir cd - Google Search

Explore your local man pages, you probably have a man 1 intro or similar which lists the available commands. (Actually the MacOS one seems rather uninformative.)

http://en.wikipedia.org/wiki/List_of_Unix_programs also collects a good sample in a convenient format.