Quote from Maverick74:
Combine is a term used in the NFL. They do combines for all the college players that were not good enough to get drafted in the NFL. Combines allow guys to attend workout sessions and let teams get a second look at them. If coaches like what they see, they sign on to training camp. A combine is a process. A process to get a second chance, a process to get discovered. A process for guys to get a second look.
actually the NFL combine is at the end of February before the April Draft and all the top college players are invited.