A free body diagram is also known as a force body diagram. It is the graphical representation of the graphical illustration used to visualize the applied forces, movement, and the resulting reaction on a body in the given condition of the body or any structure.
This diagram shows the relation between the given body and other connected body with them in moments, force applied as well as reaction by those bodies.
Example,
Let us draw free body diagram of the the car standing on the slop.


Also Read,
What are the different types of surveying?
What is Aqueduct? – Irrigation
What are the disadvantages of Reinforced concrete structure?