Of the two, mediation is a more informal process for resolving a dispute. The mediator is a neutral third party who helps the parties negotiate a resolution to their dispute. The mediator listens to both sides and offers suggestions that are supposed to help the parties come to a resolution. The advantage to mediation is that, since both parties participate in resolving the dispute, they are more likely to carry out the settlement agreed upon. A disadvantage to mediation is that the parties may not be able to come together on an agreement and will end up in court anyway.
Arbitration is a more formal process for resolving disputes.
Arbitration often follows formal rules of procedure and the arbitrator may have legal training that a mediator does not. The arbitrator is a neutral third party, but should have some expertise in the area that is the subject of the dispute. The parties should agree on who the arbitrator will be or on how he or she will be selected. Unlike a mediator, the arbitrator has the authority to make determinations and decisions that are binding on the parties. The arbitrator's job is to listen to both sides and then make a decision that is mutually binding on both parties.