Uniform motion refers to the motion of an object at a constant speed. This means that the object covers equal distances in equal intervals of time. Hence velocity of the object is uniform and velocity time graph of the object is a straight line parallel to the time axis.

Non-uniform motion, on the other hand, refers to the motion of an object at a changing speed. This means that the object covers unequal distances in equal intervals of time. This variation in speed can be caused by a change in the object's velocity or direction of motion. So velocity of the object is non uniform and velocity time graph of the object is a curved line.