From BEAM Robotics Wiki
1) A circuit, motor, LED, or similar device(s) that are connected to the output of a power source such as a solar cell, battery, or motor driver.
2) The amount of power consumed by the circuit, motor, etc.
3) Any type of weight or force that is carried by, or that is working in opposition to the actions of, a robot or any of its constituent systems, mechanisms or component parts.
For a complete explanation see the following: