Speed and Velocity
Distance and Displacement
The total length of the path covered by a body is the distance traveled by it. But the difference between the initial and final position vectors of a body is called its displacement. Basically, displacement is the shortest distance between the two positions and has a certain direction. Thus, the displacement is a vector quantity but distance is a scalar.
Speed & Velocity
The rate of change of distance with time is called speed but the rate of change of displacement is known as velocity. Unlike speed, velocity is a vector quantity.
For 1-D motion, the directional aspect of the vector is taken care of by putting + and – signs and you do not have to use vector notation for displacement, velocity and acceleration for motion in one dimension.