Every small child learns to negotiate – one more biscuit, another hour before bed, etc. Seemingly this ancient art is hardwired for humans.
At its best negotiation involves two sides discussing a problem and constructively creating the best solution. Often, negotiation in the face of conflict falls short of this standard. People make decisions in the absence of information, or without considering all the options. One side may be more powerful or have better resources. This can result in an unequal agreement.
Often when parties are stuck in a dispute they can only see win /lose options. It is this attitude that they bring to the negotiating table. In a mediation, the mediator is there to help the parties move through this to a productive negotiation resulting in a durable solution.