There are many sources of information on UNIX, its commands and services. Some of these include: the Internet, books, magazines, etc.
Below are a couple of easy ways to get the information that you need.

On the System ... the man command - the man command (stands for manual) gives you a print out of an on-line manual page. Most system commands can be found this way. To use the man command, you type the man command at the Atlas prompt, followed by the name of the command you want to find information about. For instance, if you want to find information about the rm command, you would type:
man rm

On the Net ... There are web pages out on the Internet that are totally devoted to UNIX and UNIX commands.
Some of the addresses you might find of interest are:

1. UNIX 101 - Learn more about UNIX and explore the functionality of monthly featured commands.
2. UNIXHelp for Users - Steps to getting started through programming.
3. Getting friendly with UNIX - It is just as is sounds, only better! If you are actually working on a UNIX machine, you can use this as a tutorial.
4. Search the web for "UNIX Commands" with Webcrawler or Altavista.

In Books ... A great book to delve into when it comes to UNIX commands is UNIX in a Nutshell by: O'Reilly & Associates. It can be found in almost any bookstore. This book will give you comprehensive details on most UNIX commands. It contains all the optional extensions, information about various shells, information of the vi editor, the awk scripting language, etc. It is a must have for anybody that plans on learning a lot about UNIX.

*NOTE: If you find yourself wanting to learn more and more about UNIX, there are a wide range of books out there to teach yourself. In general, if you learn a lot about UNIX and start to learn other things such as the Perl scripting language, or anything related to UNIX, the O'Reilly books are usually a safe bet.