The cavalry were soldiers on horse back.I would like to improve the answer of the former contributor asfollows:Only the Saxons had mounted infantry ("soldiers on horseback")because they used horses for long ranges troops displacements, asthey did concentrating their forces from York to London after thebattle of Stamford Bridge, in order to reach in timethe zone of Hastings before the Norman's Army could effectivelyland and consolidateitself. Indeed we should say it was heavy infantry.On the Normans side there was about one quarter of the armyconsisting of an elite, well armed and protected cavalry corp thatunlike the Saxons who fought exclusively on foot, was an integralpart of Norman (and generally said of French) way of fighting atthat time.