The judiciary is one of the main systems of courts that interprets and applies the law on behalf of the state. The judiciary of an state is responsible to provide a mechanism for the resolution of disputes of any nature -- civil, criminal and administrative. A judiciary generally does not make law (which is the task of Legislation) or enforce law (which is the duty of the Executive), but rather its responsibility is to interpret law and infers it to the facts of each case. The usual task of this branch of the state is to ensure equal justice under law. Along with a number of the lower courts, it typically comprises a court of final appeal, called the "Supreme court" aka "Constitutional court".
Don't you want to know how judiciary works, what are its tasks, when it comes into action, who are tasked to make it function, etc.? If so, check out a wide assortment of Books on Judiciary assembled here in this category, encompassing everything related to Judiciary.