General Question about Lockers

I am new to the forums and have been reading and learning a lot about the off road world. I was just wondering if someone could explain to me what exactly a locker does. I have a 1983 GMC K1500 Truck that I am looking to make into an off road truck. I have been looking at the lockers for quite some time now and I just have a few questions about them before I buy one.

If I put a locker in the rear does it make it really difficult to turn and does it wear the tires down faster?

If I put a locker in the front but run it out of four wheel drive while in driving in town will it still have the front end locked up or will it just free wheel?

Is there any particular locker that is better than another?

This truck pulls heavy trailers around a lot and I dont know if that will have any effect on what I should decide to do. I am mostly thinking of putting the locker in the front and buying a posi-trac rear end for this truck so if anyone can tell me what effects the locker in the front will have on my daily driving experience that would be great.

I also have a 1986 Chevy Silverado Show Truck that I built from the ground up so I have been around the car scene and know quite a bit about it...its just I went down with the 1986 and now im ready for the other extreme.

Thanks for the help.
Wayne