Negotiation: A method by which people settle differences. It is a process by which compromise or agreement is reached while avoiding argument and dispute.
Mediation: An intervention in a dispute in order to resolve it; mediation is a form of alternative dispute resolution (ADR), a way of resolving disputes between two or more parties with concrete effects.
Arbitration: A technique for the resolution of disputes outside the courts, where the parties to a dispute refer it to one or more persons (the "arbitrators", "arbiters" or "arbitral tribunal"), by whose decision (the "award") they agree to be bound.