Although vapor and gas are frequently used interchangeably, vapor often carries the connotation of gaseous matter in a state of Equilibrium with identical matter in a Liquid or Solid state below its Boiling point. See the entry on Vapor pressure for more information on this topic.
The constituent atoms or molecules of a vapor possess vibrational, rotational, and translational motion. More information can be found under the entry of the Kinetic theory of gases.