Your JEE Main score helps you get admission in B.Tech colleges. Different colleges have different cutoff scores based on the branch and category. If your score is above the cutoff, you can get a seat in that college. Top IITs and NITs need very high scores, while state and private colleges have lower cutoffs. After results, counselling is done where you choose colleges based on your score and rank. So, your JEE score decides which colleges you are eligible for.