A student athletic trainer is like an athletic trainer, but with no pay and less medical training. In a high school setting, they basically get water, pass out band-aids, help with treatment, and hang out with athletes. They generally spend the most time on football and other male sports, because most student trainers are females and most female athletes are bitches.
See that smokin' chick over there? She's a student athletic trainer. I'm going to get hurt so I can talk to her" " Do it man!"