what's the difference between a cassette and a freewheel?

it turns out I actually have side pull brakes on the front and rear. just looked at it, after google imaging what the different types of brakes are. what sort of brakes would be suitable upgrades without going to disc brakes?

as far as JJ's, I've been delivering for 7 months, so I know the area really well. as far as the bike, this is my bike. I like it, and I'm sticking with it. keep in mind, my bike before this was a really heavy mountain bike I borrowed from my dad...this thing feels like a feather, and turns like crazy. so, I'm happy with it. I'm not out to win the Tour De JJ, or anything...as Shp4man said, I think my Raleigh is a cool bike. plus, it just fits me. I tried out a number of bikes when I was going through this guy's shop, and I knew with in seconds after I got on, the Rapide was the one I was going to be leaving with.