The NCAA Division I Basketball is divided into different conferences. There are approximately 350 men's and women's teams in each of 32 conferences and during the regular season, teams play games both inside and outside their respective conferences.
A team usually plays approximately 16-18 games in its respective conference. However, the rules vary between the individual conferences and there are sometimes significant differences. The remaining non-conference games can be organized and scheduled by the schools themselves.
The 32 Division I champions and 36 wild card teams qualify for the final NCAA March Madness tournament at the end of the season. Decisive for a qualification is the Winning Percantage within the own division, the Strength of Schedule of the respective team and further factors, which are considered with the appointment.
Sources:
1. NCAA March Madness: https://www.ncaa.com/news/basketball-men/article/2021-01-15/how-field-68-teams-picked-march-madness
2. NCAA Strength of Schedule: https://www.ncaa.com/news/basketball-men/article/2019-01-16/explaining-college-basketballs-strength-schedule
3. NCAA Division I Basketball Wikipedia: https://de.wikipedia.org/wiki/NCAA_Division_I