An object at rest has zero velocity and will continue to have zero velocity in the absence of an unbalanced force. Unless acted on by an unbalanced force, such an object will not change its state of motion (i.e., velocity).
When an object's speed remains constant - it does not increase or decrease - we say it is moving at a constant speed.
Acceleration is a vector quantity defined as the rate at which an object's velocity changes. If an object's velocity changes, it is accelerating.