Why are there so few "running" processes?

On all of BSD/Linux/MacOS and Solaris, I made an observation - no matter how busy the system is, top always reports very few (usually 1-2) running processes. According to my limited understanding, a process is in "running" state if it is using CPU time, or waiting for CPU time to become available. So, here is a scenario: I use SSH to tunnel VNC, then run top on remote machine, in a Terminal emulator: - top itself is listed as a "running" process (understandable) - sshd is listed, but not "running" - Xvnc is listed, but not "running" But sshd is tunneling VNC traffic, Xvnc is what keeps me updated with screen content, how can they not be using CPU time? If they are using CPU time, then how come they are not "running"?