Like it sounds...
Self-defense is, well, self-defense. How break bearhugs, throw people of they RNC you while standing, and so-forth. Might be expanded to include striking and such, making it more Krav Maga-ish. Basically traditional jiu-jitsu with BJJ theory.
Sport BJJ is focused on competition. Not all the techniques would be very smart to pull of on the street. Most schools will still show a few self-defense techniques, but that will probably be less than 5% of the time. After you get good at sport BJJ though the self-defense is extremely easy to figure out (you'll know the theory and likely instinctively react correctly, even if you weren't shown how to respond in a specific situation).
MMA is going to be no-gi and combine punching/kicking. Usually those schools are BJJ and/or wrestling with muay thai and/or boxing. Depending on the school it could be "hard core", where people are training for competition, or "lighter" where they do situational drilling.