When the computer first turns on, it enters different run levels when the computer runs a Unix system.
The run levels on a standard Linux System are:
1: Single User
2: Multi User no Networking
3: Multi User with Networking (typical for servers)
4: User Define
5: Multi User with Networking and GUI
A computer starts at run level 0 when it is off. When the user turns it on it will go from 1-5 for a desktop computer, or 1-3 on a server. When the user tells the computer to reboot it goes into run level 6.
You can use the
init command (as root) to change the run level, though this is