Re: different type of hitch:
Lets look at the types of 3 point hitchs:
Position: Holds a absolute point in referance to the tractor: As it leaks down, it will repoistion it's self to maintain a level according to the tractor. A two foot furrow will be a two foot furrow on level ground. As the tractor noses down, the plow comes up. Etc.
Draft: Holds it's poisition to a reference point to the tool. The tool makes the reference. A 2ft furrow will be a two foot deep furrow. (within reason)
Set: the tool "stays" where you put it. Like the Position, but it won't self maintain. As it leaks down the depth increases.