Check out this post: http://www.mavromatic.com/2007/03/diy-part-i-replacing-rear-rotors-and-brake-pads-on-a-land-rover-discovery-ii/
Brake rotors wear because during use, brake pads are pushed against them while the rotors are turning. It's the friction between the moving part and the staationary part that slows the vehicle down. Pads wear too, usually quicker. Brake rotors wear due to use, they are considered a service item.
The hubs basically. But usually you won't see the hubs, they'll be hidden by the brake rotors or brake drums.
Front rotors are round metal plates / disc. Hence the term, "Disk Brakes" They fit onto the axles behind the wheels and are part of the brake system. Specifically they are the part that the caliper/brake pad assembly applies pressure to, to create the braking action.
It's a good idea. Typically, when you have brakes done at a garage, turning the rotors are part of the deal. If you don't turn the rotors, imperfection in the rotor surface can create grooves and uneven wear in your new pads.
Brake rotors are subject to a lot of heat and wear. After a period of time, they warp and have to be "turned". turning the rotors actually makes them thinner so they won't last as long as they did. Everytime they are turned, the thinner they get. There is a point where they are too thin to safely use. That point is stamped on the rotors and it is illegal for someone to turn past them that point. Rotors are not expensive and your brakes are the most important part of your car. I wouldn't skimp on my brakes.
The brake rotors for the 1999 Montana and 2007 Town & Country are different part numbers and different dimensions; therefore they will not interchange.
Check with local parts store to see if they are the same part
Normally it means to bring it back to factory specs. An example would be to machine brake rotors. They would pretty much cut the rotors with a machine to get them back to factory specs.
The front brake rotors are warped. It's not the power steering pump if it only happens when braking. One or both of the rotors need to be replaced. Overheating causes this, especially if the rotors are old or have been turned as part of a previous brake job on the truck.
It depends on the current condition of your rotors really. If they aren't worn down too badly (if there is a big lip on the outer part and dipping in closer to the center) or aren't rought or jagged than you should be fine. Rotors tend to last longer than pads in general. If they are jagged or rough than you need to change them or they will eat away your pads much quicker than they should.
See related link, nothing special about the rotor when you get to that part of the brake job, just slide the old ones off and slide the new ones on (see detailed description of brake job with pictures in link). This is a very easy job to do yourself.