A third party decides on a dispute to resolve it, delivered by an impartial, neutral person who considers the arguments of both sides and makes a decision based on current evidence. It's quite formal, governed by The Arbitration Act 1996 which many contracts have within a Scott v Avery clause. This outlines that, should a dispute arise, both parties agree to use arbitration methods to settle their dispute. Before it goes ahead it's agreed that the arbitrators decision is final, meaning there's limited right to appeal bar cases of serious irregularity of conduct.