Whenever you use Unix, you are running a program. The program you are running when you're not running anything else is called the "shell". It's pretty much the equivalent of "the Finder" on the Mac/IIGS or the Applesoft prompt from the old days. The shell you're using is (hopefully) the "C-shell", so called since its syntax is similar to the "C" language. The name of the program is "csh" (but you don't really need to know that now).
When you're in the shell, you get some sort of prompt. Often this is the name of your computer followed by a special character, like "%" or ">". The whole prompt might look like this: "uranus>". This would mean that you are using a computer called "uranus", and the shell is waiting for you to type something. (Note: prompts vary widely. Your prompt may be quite different.)
What you do at this prompt is type the name of a program you want to run. Then the shell runs the program. When the program is done, you're back in the shell. Now, some of these programs are things you would think of as "commands". Well, they are. You type their name, something happens, and then you're back in the shell. For example, type "ls" and press <return>.
Note: From here on, I'll use "%" to indicate that something should be typed in the C-shell (this is a Unix tradition; there are lots of other Unix traditions, and I wish I knew more about them -- I'd probably understand a lot more of what is going on if I did). So, using this convention, type
% ls"ls" is the name of a program that does the equivalent of a "CATALOG" in ProDOS or "DIR" in MS-DOS. You can think of it as a command or as a program you run -- really, it's both.
Lots of programs/commands have "options" you can give them, to change what they do. Many of these are signaled by a dash. For example, if you want detailed information about the files in your directory, you can type
% ls -lThe "-" signals an option, and the "l" stands for "long". You should get something like this:
total 39 -rw-r--r-- 1 chappell 123 Aug 24 1990 -i drwxr-s--- 3 chappell 512 May 2 13:01 News/ drwxr-S--- 2 chappell 512 Apr 2 16:51 backups/ drwxr-s--- 4 chappell 1024 Apr 30 14:17 cfiles/ -rw------- 1 chappell 1731 May 2 13:46 dead.letter -rw------- 1 chappell 25717 May 2 13:33 mbox drwxr-s--- 4 chappell 512 Apr 30 15:02 misc/ drwxr-s--- 2 chappell 512 Apr 30 15:00 per/ -rw-r----- 1 chappell 2005 May 2 13:32 temp -rw-r----- 1 chappell 1731 May 2 13:46 unix.tut drwxr-s--- 2 chappell 512 Apr 2 14:49 utilfiles/The first column has to do with "permissions" -- who has access to your files and what they can do with them (r = "read", w = "write", etc.). The name is who owns the files (should be you). The number after that is how many bytes the file uses. Then comes the creation date/time and finally the file name. (Yours may have a bit different format -- these things vary some from system to system).
Another option for the "ls" command is "-a", where "a" stands for "all". Certain files in your directory are normally invisible. These are usually files that you won't have to deal with on a day-to-day basis, which would just clutter up your directory listing. A file is invisible if its name begins with "." -- normally. You can see them by typing
% ls -aThis should give you a listing of all your regular files, plus several files beginning with ".", like ".", "..", ".cshrc", ".login" and maybe a few others.
Now, you can usually combine options. To see detailed information on absolutely all your files, you can type "ls -a -l" or "ls -l -a". With some commands (like ls) you can put several options after just one dash: "ls -al" or "ls -la".