What are these features for on the back of my power supply?

Most power supplies have the following four features visible on the rear (see image below):

Exhaust fan and grate
AC input
0-1 Power toggle switch (zero is off, one is on)
115-230 Voltage slide switch (use 115v only in USA, 230v only for use in Europe)

Some power supplies have additional features visible on the rear (see image below):

Fan control slide switch (A[1]:Automatic or system controlled, L[2]:Low cooling, M[3]:Maximum cooling)
Turbo button (ramps up fan RPMs, another method of providing additional cooling, not pictured)
AC ouput (only recommended for low power-consuming devices like stereo speakers)