I've had my battery out for three weeks. Will it have to be charged before I put it back in? Also motorcycle batteries confuse me. They seem alot different and more high maintenance, with the water level and all. Why is that?

Well, they prolly seem more confusing because they are not the sealed "set it and forget it" type maintenance free batteries that we are used to it our cars. The old car batteries used to be like that but they've come a long ways. There are "maintenance free" motorcycle batteries too, you just don't have one 

And you'll prolly need a charge. Motorcycle batteries are pain in the tail. haha, get it. the tail. *rimshot*

It's just the type of battery.  Car batteries are sealed batteries.  You can get one for your bike.  As for you charging the batt up, no need.  three weeks is nothing.

I leave it disconnected twice a year for about one month each time.  I don't recall having to charge it because of that.  HTH.

Cheers,
e.