Litigation is a form of dispute resolution. Unlike ADR litigation involves a judge who has the authority to make decisions. Each party is represented by a lawyer to argue their case. Unlike mediation or conciliation, litigation is not voluntary or confidential and can take a long time to resolve.
In mediation, disputes can be resolved in one day and at very little cost to the parties. Litigation is a process known to destroy the relationship between the parties whereas mediation and other ADR processes seek to preserve the relationship. Parties often enter into litigation under the premise that they will have their day in court, be victorious, humiliate the other party and walk away vindicated and richer.
These outcomes are rarely achieved. It is the costliest dispute resolution process in current times. The process has rules and procedures governed by law. The judge makes his decision based on evidence and the argument put forward. It results in a win/lose outcome. In litigation, any decision is binding on the parties where as in other ADR processes it is not. Further reading http://en.wikipedia.org/wiki/Litigation