Freewheel?

So I'm going to be purchasing all the stuff for my bike soon, and I've read that I need a wide crank. I saw that SBP sells them...but it talks about a freewheel. Isn't the freewheel the thing that makes it possible to pedal backwards (or not pedal) while riding? Do I need one on both the pedal side and on the wheel? I'm buying worksman wheels from pirate cycles, and noticed they have a 7-speed freewheel. Is it hard to install?

Also I've heard talk about pirate cycle's sprocket adapter...what exactly does it do?

Thanks!

Well I'm starting with a Schwinn Clairmont 7-speed. I'll be replacing the fenders, seat and adding lights.

I'll be buying the alloy worksman wheel set from pirate cycles (the front has a drum brake on it, so I'll use that and just leave the original brake on the back...it's pretty strong.)

I haven't decided on tire/innertube combination yet (suggestions?)

I'll be using the HS + Qmatic kit from BlowByU.

Is there anything else I need? Eventually I'll be upgrading the engine with parts from AGK, but I'll wait on that for a little while first