What kind of cat has the tip of one ear missing?
A cat can be missing the tip of an ear because it was in a fight and it got damaged (not unusual) or it was part of a TNR program where they clip the tip of one ear to signify the cat was neutered/spayed before being released back into the wild or a cat colony. (TNR = Trap, Neuter, and Release)
an alley cat most likely. that is from fighting, it's not a breed of cat
ferals that have been spayed are neutered. This is a widely recognized marker throughout North America. They also have had at least their first round of shots (rabies, FIV, etc)
Some vets will clip one ear when a cat has been spayed, especially done for feral cats as it is easy to be identified and doesn't require to be caught