part newbies
- they sign/cut straight up rookies all the time and try to raise them up within the WWE style. i see why they do this but i'm not particularly fond of it as it limits their skillset.

part established/developing talent
- to either get them used to WWE style wrestling/presentation or get them in shape for a main roster run. or just figure out a workable gimmick for experienced people and see if they can work in the WWE.

part vets
- they get some former WWE people like Rhyno just to throw em some cash and keep it in the family. or they get people like Sara Del Ray to train the current talent

then sometimes main roster people do an ep or 2 of NXT just so they can see how some of the promising talent has come along. Cesaro has some amazing matches on NXT.

what else am i missing? i think that covered it all.