WHAT DOES A COUNTY COMMISSIONER DO?

I can't tell you how many people have asked me this question. The office is set by the Texas Constitution, Article 5, Section 18 b):

Each county shall, in the manner provided for justice of the peace and constable precincts, be divided into four commissioners precincts in each of which there shall be elected by the qualified voters thereof one County Commissioner, who shall hold his office for four years and until his successor shall be elected and qualified. The County Commissioners so chosen, with the County Judge as presiding officer, shall compose the County Commissioners Court, which shall exercise such powers and jurisdiction over all county business, as is conferred by this Constitution and the laws of the State, or as may be hereafter prescribed.

Richard O. Avery and Stacy Morris wrote a great one page article that tells it way better than I can.