Motion planning is a term used in robotics

Robotics

Robotics is the branch of technology that deals with the design, construction, operation, structural disposition, manufacture and application of robots...

 for the process of detailing a task into discrete motions.

For example, consider navigating a mobile robot

Mobile robot

A mobile robot is an automatic machine that is capable of movement in a given environment.-Overview:Mobile robots have the capability to move around in their environment and are not fixed to one physical location...

 inside a building to a distant waypoint. It should execute this task while avoiding walls and not falling down stairs. A motion planning algorithm would take a description of these tasks as input, and produce the speed and turning commands sent to the robot's wheels.