Yes, rest and motion are relative terms; a body can appear to be at rest to one person while appearing to be in motion to another.
Consider a moving train and a person standing on a platform. The passengers in the train are in motion with respect to the person on the platform. A passenger in the train will observe the fellow passenger to be at rest.
Thus, same object or body may be at rest or motion depending on the observer. Thus, rest and motion are relative terms.