Linux’s runlevels are:
The term runlevel refers to a mode of operation in one of the computer operating systems that implement Unix System V-style initialization. Conventionally, seven runlevels exist, numbered from zero to six; though up to ten, from zero to nine, may be used.
Depending on your distribution runlevels may differ
Whick runlevel am I in?
So, to find out which runlevel are you In just run:
You will get something like this:
run-level 3 2010-12-11 21:09 last=S