A more thorough explanation:

A Justice of the Peace (JP) is a type of judge who handles minor legal matters such as small claims actions, traffic violations, and misdemeanors in "justice courts." They have limited jurisdiction and authority, often on the local level and restricted to criminal cases.

Originally from English common law, JPs were common until the 1950s. Nowadays, they exist primarily in rural "justice districts" where it is unreasonable for the public to travel to the county seat for trials of minor matters.

For example, in Nevada, JPs are lucrative jobs since they perform many of the marriages of elopers from other states, as Nevada has no waiting period from license to wedding. A JP is usually an attorney, but some states still allow laypersons to qualify by taking a test.

Overall, a Justice of the Peace is a local judicial officer who has jurisdiction over minor criminal offenses and minor civil disputes, and authority to perform routine civil functions such as administering oaths and performing marriage ceremonies.