TER are regional trains operating all over France. They run on secondary lines, connecting small villages with the main lines and larger cities as well as assuring fast city-to-city connections on main routes with fewer stops (but not as fast as TGV or Intercités services).
A large variety of trains is used to assure these services. Most trains are quite modern though, with air-condition and low-floor entry. Most services are 2nd class only however especially on semi-fast services on longer distances you will also find 1st class seats.