The Scout Line of Light Cavalry consists of lightly armed, but very fast riders. Sixteen of the eighteen civilizations in the game receive one or another form of this line as a starting scout unit. Light cavalry typically carry a bonus against Priests and have pierce armor to assist in riding down archers, but are not exactly equipped for a general melee. It is available at the stable, and includes the Pathfinder, the Light Cavalry and the Hobelar.
The Breton Gwaster and Kigner is also considered a Light Cavalry unit, as is the Polish Szlachcic, which gradually becomes a heavier unit.