speed and velocity
speed is a scalar quantity and velocity is a vector quantity , that means speed is only based on magnitude , but have no direction ,while velocity is based on magnitude as well as direction . for example : there’s a circular path and you are cycling and your speed is suppose 6m/s but in terms of velocity your direction keep changing as each point in circle ‘s circumstance denotes a different direction.
Even if your magnitude is the same but your direction keeps on changing so your speed is same but your velocity keeps on changing through out . And also change in velocity is called acceleration .
another example suppose you moving in a straight path in a speed if 1m/s but you turn back and start moving the opposite direction so even if your moving in the same speed you direction changed , so thus your velocity