Challenge for cause
A challenge for cause is a request from a party to a judge that a certain prospective juror not be allowed to be a member of a jury because of specified causes or reasons.
For example, a potential juror in a murder case, where the death penalty is being sought, states that she cannot ever vote for the death penalty for religious reasons. In such a case, both attorneys (and often, the judge) will question the potential juror to determine if that is the case.
If so, the challenge is granted. It is not counted against the number of peremptory challenges that one side or the other are granted.