These are those who have graduated from the school and are chosen to join the X-Men. All X-Men share a common goal: to fulfill Xavier's Dream. Their goal is to have mutants and humans co-exist peacefully, just as Charles Xavier wanted. Most X-Men belong to the school's faculty, whether it be teaching or cooking. X-Men are usually above twenty years old. There are usually no more than twenty members at one time.

X-Students are mutants who have found their way to the school. They undergo education similar to normal students, but have special classes to fit their powers. Their powers are not as refined as the X-Men. The school offers education for students of all ages. They have to sit through a final exam each year to determine if they are capable of moving up a grade or graduating. There is no maximum number of X-Students.

These are a group of mutants who share a common goal of mutant superiority over humans. The Brotherhood was formed by Magneto. They plan to achieve their goal through belittling humans or completely eradicating them. The X-Men usually stand between them and their goal.

These are people who don't have anything to do with the X-Men or Brotherhood. People in this group can be mutant or human and can have normal jobs like officer, medic, salesman, etc.