Motion planning deals with the problem of moving the arm to a configuration, allowing you to reach a pose with the end effector without crashing the move group with any obstacle, that is, the links themselves or other objects perceived by sensors (usually as point clouds) or violating the joint limits. The MoveIt! user interface allows you to use different libraries for motion planning, such as OMPL (http://ompl.kavrakilab.org), using ROS actions, or services.

A motion plan request is sent to the motion planning module, which takes care of avoiding collisions (including self-collisions) and finds a trajectory for all the joints in the groups that move the arm so that it reaches the goal requested. Such a goal consists of a location in joint space or an end effector pose, which could include an object (for example, if the gripper picks up something) as well as kinematic constraints, such as position, orientation, visibility and user-specified constraints.

The result of the motion plan is a trajectory that moves the arm to the target goal location. This trajectory also avoids collisions and satisfies the velocity and acceleration constraints at the joint level.

Finally, MoveIt! has a motion planning pipeline made of motion planners and plan request adapters. The latter are components that allow the pre-processing and post-processing of the motion plan request. For example, pre-processing is useful when the initial state of the arm is outside joint limits; post-processing is useful to convert paths into time-parameterized trajectories.