Hedge Knight

"Hedge knights, now, are a different breed. Take a sellsword and remove the sense. They get their name from where they sleep: under the hedges of the Nine Kingdoms and ditches and stables. They do not have the family name or the purse like real knights, so they spend all their money on armor and a horse and riding tourney after tourney in the hope of impressing some lord or winning some prize." 
― Ser Allister Crowe.
Hedge knights are independent knights who wander the Nine Kingdoms seeking employment with major lords and nobility. They are so-called because it is said they are so poor that they cannot afford to stay at inns, but sleep under hedges by the roadsides. They also sleep in ditches and stables.
Unlike knights who are are sworn to the service of a lord, they have little money and no family name. For this reason they spend what money they have on armor and a horse and ride in tourneys in the hope of impressing a lord and being accepted into his household, becoming a sworn sword, or winning a prize.