A lighter is a type of cargo vessel. Lighters load cargo from larger vessels. This may be to allow them to reduce their draught to enter a particular port, for trans-shipment of the cargo into coastal waters which can't directly service ocean-going vessels, or as temporary capacity, such as a small oil tanker attached to an oil rig. They may occasionally be equipped with some processing capability.
Military lighters carry forces to land where no friendly and accessible ports are available (see landing craft).