This is from the NCAA rulebook.
The head coach of either team may request that the game be stopped and a play be reviewed by challenging the on-field ruling.
1.
A head coach initiates this challenge by taking a team timeout before the ball is next legally put in play (Exception: Rule 12-3-6-d) and informing the referee that they are challenging the ruling of the previous play. If a head coach’s challenge is successful, they retain the challenge, which may be used only once more during the game. Thus, a coach may have a total of two challenges if and only if the initial challenge is successful.
2. After a review has been completed, if the on-field ruling is reversed, that team’s timeout will not be charged.
3. After a review has been completed, and the on-field ruling is not reversed, the charged team timeout counts as one of the three permitted that team for that half or the one permitted in that extra period.