The document asserts that the judge cannot be impartial due to a personal bias, conflict of interest, or prior relationship with one of the parties.
This is a serious legal step that must be backed by specific facts, not just a disagreement with the judge's prior rulings. If the affidavit is successful, the current judge will recuse themselves, and the case will be reassigned to a new judge to ensure a fair and impartial trial. In some jurisdictions, a "peremptory" affidavit of prejudice allows one automatic change of judge without needing to prove specific bias.