The human body perceives body movement and controls balance primarily from the vestibular, ocular and its own sensory systems. Motion sickness occurs when the different sensory systems of the body do not have the same information about motion and conflict.
For example, when we are riding in a car, our body feels the bumpy motion, but our eyes look at the car is relatively stationary, the vestibular system in the ear feels different information, then the brain receives these mixed information, creates a conflict, and the body has discomfort symptoms such as dizziness, nausea and vomiting.