Division 1
79 programs.
For the most serious athletes. 
Year round commitment: regular practices and training during the off season.
Scholarships available to the top recruits. (Not applicable to Ivy League schools as they do not offer scholarships).

Division 3
165 programs.
For the less committed athlete (but no less serious or skillful).
In season commitment: regular practices and training in season only. 
No scholarships available, making it possible for the athlete to participate in other sports.

*Division 2 schools offer a middle ground between D1 and D3. There are very limited scholarships available for athletics, but the required time commitment is often less that that of a D1 school.