The Pegasus Knight is a unit class who fights on a flying Pegasus mount with a spear. These characters have the ability to fly over normally impassable terrain for long distances, a natural ability to fear should you be facing air units. Pegasus Knights tend to have very low defense and health, making them a little more fragile than other characters. Their high speed is their only saving grace, easily avoiding attacks.
The Pegasus Knight may seem fragile, but they are one of the most useful classes to have on the field. Their ability to fly giving them obvious advantages over opponents and the ability to use the rescue command in later Fire Emblem titles allows them to be used as a type of transport for ground units. When attacking, it is always important to pay attention to your enemies. Pegasus knights are weak against archers, and the accurate magic of mages is more than enough to tear through what little health they have.
The Pegasus Knight was originally promoted into the Dragon Knight, but these classes were eventually separated into two entirely different jobs. Currently, the Pegasus Knight upgrades into the Falcon Knight.