Tennessee is a US state in the South. As in most American states, automobiles are the primary form of travel. In larger cities you will find public bus systems, and Greyhound buses are an option for travel in between cities. There are also major airports in all large cities (Nashville, Memphis, Knoxville, Chattanooga, and the Tri-Cities) and many smaller airports scattered across the state.
Unfortunately there is no option for rail travel to the central or eastern parts of the state. However, Amtrak runs the fabled "City of New Orleans" line through Memphis and Newbern. This is certainly worth considering if you are planning to visit those areas, especially if you are heading along the Mississippi River. Also, the city of Nashville operates a commuter rail from the suburbs to the downtown area.