Light ships are ships that can only equip M1 satellites. These usually have little room for modules, but are small, agile and fast.
Due to their low number of hitpoints, a single salvo of a heavy ship will often take them down. Extra armor plates, if they are not offset by inertial dampers or stabilizers, will slow down the ship too much, while speed is usually the main asset of light ships.
Therefore, for survivability, light ships often capitalize on speed, agility and the pilot's skills to evade enemy fire.