If you have a 4 lane highway, it goes:
L: Passing LM: Fast Lane RM: Cruising Lane R: Entrance/Exit lane
If you have 3:
L: Passing M: Fast Lane/Cruising R: Cruising/Exit
If you have 2:
L: Passing R: Cruising/Exit
There is always a passing only lane specifically for creating the opportunity for others to move around slow or stopped traffic, and for emergency vehicles to (in theory) have a clear path. Most people treat this as a fast lane though, and moreover, most driver’s tests do not ask you about this.