SHM- Simple Harmonic Motion:

An object moves in a Simple Harmonic Motion when its acceleration is proportional to the displacement and when they are opposite to each other.

This image above gives us a simple idea of the changes between Velocity and Acceleration.

A more graphical approach would look like this:


The velocity graph is translated by 90 degrees to the right from the displacement graph.
The acceleration graph is reflected from the x-axis.