Gurdjieff did not speak much about the movements. He wrote sparingly about them. But when he did,he gave an insight into what the movements actually are and their aim. This is a small extract to help people understand what the movements do.
You ask about the aim of the movements. To each position of the body corresponds a certain inner state and, on the other hand, to each inner state corresponds a certain posture. A man, in his life, has a certain number of habitual postures and he passes from one to another without stopping at those between.
Taking new, unaccustomed postures enables you to observe yourself inside differently from the way you usually do in ordinary conditions. This becomes especially clear when on the command “Stop!” you have to freeze at once. At this command you have to freeze not only externally but also to stop all your inner movements. Muscles that were tense must remain in the same state of tension, and the muscles that were relaxed must remain relaxed. You must make the effort to keep thoughts and feelings as they were, and at the same time to observe yourself.