Intention movements are physical indications an organism is about to move or perform an action. They signal to others that something is about to happen. Common intention movements are threat displays like bared teeth in animals or a clenched, raised first in humans. Research shows that intention movements develop in a ritualized way in which these behaviors become signs in a group that predict behavior.
An example of this would be in a wolf pack when one bares teeth and growls a another who is trying to steal food. Growing up in the pack the wolves learn that this signal means to back off because there is an intention of violence if they don't.