From BEAM Robotics Wiki
Derived from the Latin word, vehiculum, the term "vehicle" is general used to refer to a non-living means of transport. It may be self-propelled or it can be pulled by a "vehicle" that is self propelled, by an animal or by human being.
In robotics the term vehicle may refer to the platform or mechanism used to provide a robot with a means of locomotion. This can be a platform with wheels, tracks, legs, be capable of flight or of moving on or beneath the surface of a body of water.
NOTE: the plural form ("Vehicles") will often be used in reference to the imaginary creatures described by Valentino Braitenberg in his book "Vehicles: Experiments in Synthetic Psychology" (1984, Cambridge, MA: MIT Press) in which he explains his theory about how complex behaviors result from simple sensory-motor interactions.