Uniform Speed: If an object covers equal distances in equal intervals of time than the speed of the moving object is called uniform speed. In this type of motion, position –time graph is always a straight line.
Instantaneous speed: The speed of an object at any particular instant of time is called instantaneous speed. In this measurement, the time ∆t→0.
When a body is moving with uniform speed its instantaneous speed = Average speed = uniform speed.