Distance and displacement
Distance is a scalar measurement of how far something has moved. It’s the length of the path something follows from A to B.
Displacement describes the separation of two points. In other words, it’s the distance from A to B “as the crow flies”. However, because displacement refers to a length in a particular direction, it is therefore a vector quantity.
Speed and velocity
Speed and velocity relate to distance and displacement, respectively.
Speed is a scalar measure of the distance moved per unit of time:
Velocity is a vector that measures change in displacement per unit time:
Acceleration
Acceleration is the rate of change of velocity with time:
The units of acceleration are therefore m·s-2.