“Motion study” is a term for simulating and analysing the movement of mechanical assemblies and mechanisms. Traditionally, motion studies have been divided into two categories: kinematics and dynamics. Kinematics is the study of motion without regard to forces that cause it; dynamics is the study of motions that result from forces.
Kinematics is a simulation showing where all of the parts in an assembly are in time as it goes through a cycle. This technology is useful for simulating steady-state motion (with no accelerations) as well as in evaluating motions for interference purposes, reaction forces on the associated parts are also critical.
One of the reasons that solid modelling is becoming so popular it sets a foundation for so many other applications. You can now create working drawings and realistically render models that look like the real thing, and generate physical models via rapid prototyping. Similarly, studying the motion of moving mechanisms and assemblies is fast becoming an important addition to solid modelling.