It is the 'area' inside of which an oficer of the law or other potentate has legal authority as vested upon him/her by the local government to enforce laws, ordinances, codes etc. In most, but not all, cases this includes the authority to detain and/or arrest (take into custody). The area in which one has authority. An A-ville police officer cannot make an arrest in B-ville for he is out of his jurisdiction. (He can, however, use the authority given to us all as citizens: Citizen's Arrest.)