A tribunal is a court or a governing entity that has the authority to settle matters within its own organization or area. Tribunals can exist in many different areas of society. For example, the military and churches commonly have tribunals. However, tribunals do not replace the need for the legal system at large.
Many organizations prefer to settle disputes within their own structure. This is why tribunals exist. For example, a military tribunal may be convened if a soldier has been accused of a crime or of a serious breach of duty. In these circumstances, the tribunal would carry out the trial in much of the same way that a normal court would. Witnesses could be called, evidence would be presented, etc. However, military officials may make the final decision of guilt or innocence instead of a jury of peers.