This link answers your question...even includes info on Division III
What's the difference between Divisions I, II and III?
Division I member institutions have to sponsor at least seven sports for men and seven for women (or six for men and eight for women) with two team sports for each gender. Each playing season has to be represented by each gender as well. There are contest and participant minimums for each sport, as well as scheduling criteria. For sports other than football and basketball, Division I schools must play 100 percent of the minimum number of contests against Division I opponents -- anything over the minimum number of games has to be 50 percent Division I. men's and women's basketball teams have to play all but two games against Division I teams; for men, they must play one-third of all their contests in the home arena. Schools that have football are classified as Football Bowl Subdivision (formerly Division I-A) or NCAA Football Championship Subdivision (formerly Division I-AA). Football Bowl Subdivision schools are usually fairly elaborate programs. Football Bowl Subdivision teams have to meet minimum attendance requirements (average 15,000 people in actual or paid attendance per home game), which must be met once in a rolling two-year period. NCAA Football Championship Subdivision teams do not need to meet minimum attendance requirements. Division I schools must meet minimum financial aid awards for their athletics program, and there are maximum financial aid awards for each sport that a Division I school cannot exceed.
Division II institutions have to sponsor at least five sports for men and five for women, (or four for men and six for women), with two team sports for each gender, and each playing season represented by each gender. There are contest and participant minimums for each sport, as well as scheduling criteria -- football and men's and women's basketball teams must play at least 50 percent of their games against Division II or Football Bowl Subdivision (formerly Division I-A) or Football Championship Subdivision (formerly Division I-AA) opponents. For sports other than football and basketball there are no scheduling requirements. There are not attendance requirements for football, or arena game requirements for basketball. There are maximum financial aid awards for each sport that a Division II school must not exceed. Division II teams usually feature a number of local or in-state student-athletes. Many Division II student-athletes pay for school through a combination of scholarship money, grants, student loans and employment earnings. Division II athletics programs are financed in the institution's budget like other academic departments on campus. Traditional rivalries with regional institutions dominate schedules of many Division II athletics programs.
Division III institutions have to sponsor at least five sports for men and five for women, with two team sports for each gender, and each playing season represented by each gender. There are minimum contest and participant minimums for each sport. Division III athletics features student-athletes who receive no financial aid related to their athletic ability and athletic departments are staffed and funded like any other department in the university. Division III athletics departments place special importance on the impact of athletics on the participants rather than on the spectators. The student-athlete's experience is of paramount concern. Division III athletics encourages participation by maximizing the number and variety of athletics opportunities available to students, placing primary emphasis on regional in-season and conference competition.