The object in motion, indicated by the heavy circle at the left side of the image, is undergoing motion at constant velocity. This means that the object is not accelerating. The short line coming off of the top of the object represents the velocity of the object (recall that velocity is a vector quantity with magnitude and direction). The first graph depicts the object's position as a function of time, in this case it is increasing at a constant rate. The second graph depicts the object's velocity as a function of time, in this case, the velocity is constant.