What do you do at an MMA class?

Basically Ive found out that theres a place near me thats teaching mixed martial arts, and I'm curious as to what they actually do in these classes, would they teach me Brazilian jujitsu and muay Thai, or is an MMA class only for people who already know these two arts and simply for MMA practitioners to practice?. At the moment I'm studying taekwondo and plan to continue my study, I'm thinking of doing MMA and taekwondo. Just on different days of course.