Hello,

The NIT means National Institute of Technology and IIT means Indian Institute of Technology. If you are qualified the JEE Mains examination with good marks then you got NITs for admission. But it's all process going though the counselling. For alloted NIT college you have to admission there. And after qualifying the JEE Mains examination you have to apply JEE advanced examination. And if you qualify this examination then you have to chance to get IITs colleges but through counselling ofcourse. So you can't choose IITs or NITs colleges by your own choice.

All the best.