They CAN mean the exact same thing, but often, we think of movement as having a direction and a purpose, but we don't always think of motion like this. Motion just means it is not sitting still - it might be just restless, thus having no purpose other than not sitting still, but you can give it purpose, for example, by adding a purpose. Usually, but not always, motion implies a purpose toward, or away from something, but you still need to specify toward, or away from what/where. This might be confusing, so the simplest I can think to state it is that motion doesn't always imply a purpose, and movement usually does, but they can mean exactly the same thing.

Motion is usually a continuous change of position, by something moving at a consistent speed (for example, a train, elevator or car). Movement describes anything which moves even slightly (a blink, a shrug, a person playing a sport).