From the Texas Association of Counties:
What is a Justice of the Peace?
The justice of the peace presides over the justice court in cases involving misdemeanors, small civil disputes, landlord/tenant disputes and more. They also conduct inquests and may perform marriage ceremonies.
What Does a Justice of the Peace Do in Texas
A justice of the peace in Texas has the following duties:
Hears traffic and other Class C misdemeanor cases punishable by fine only
Hears civil cases with up to $20,000 in controversy