There are multiple distinct password realms within the department's computer systems. What this means is that you may need to keep track of up to three separate passwords, and keep track of when to use each one. It's important to be aware that a password that works on one machine may not work on another machine.
It's also important to pay attention when reading instructions. You may see reference to your CS Kerberos password, CS windows password, or UMD Directory ID. These are distinct passwords, unless you happen to have set them to the same thing.
Some department subsystems (e.g., the forums, wikis, and subversion server) may also use their own internal authentication mechanisms. This means even more passwords to keep track of, but in many cases this allows for easy collaboration with people who do not have regular department computer accounts.