Privileges & Partions questions..Please Help!


I notice that I when I "get info" on certain folders (sites, music, movies, pictures, & public) in OSX they have strange members attributes.

The privilege options say members of group "Wheel" and/or memebers of group "Staff". What and/or who are "Wheel" and "Staff"? How do i change them? Or do i need to change them?

Also, when i installed OSX i installed it on it's own partition, so i have two partitions. Problem here is: when i try to set up OSX with multiple users i cannot put privileges on the partition that OSX is NOT on. So anyone can delete files from that partition. Is there any way to change this so i can actually have multiple users use this computer without the fear they will erase valuable things?

400mhz G4 Tower (Sawtooth)
20 Gig
Studio Display (ADC)