Depends.
If it's an illuminated switch, then yes, it needs power and ground, and the center is the output.
If not, it's prolly what's called SPDT, single pole double throw.
You can use it as an on-off switch by using the center and either of the end terminals.
You can use it as an A-B switch, for instance to power two different lights, by running the power to the center and each light to one end.
They also come in center off, which has three positions: On, Off, On.
Lots of options in switches. Don't even get me STARTED on relays.
Grounding the opposite end has no real purpose if you're using it as a basic on-off, since the load will be grounded on the far side anyway =)) No increase safety and more hassle, IMHO, for the extra wiring.
-- A