When two or more forces acting on an object do not change the rest motion of that object, it is called equilibrium.

Here's a breakdown:

* Forces: Forces are pushes or pulls that can cause an object to accelerate (change its motion).

* Equilibrium: A state where the net force acting on an object is zero. This means all the forces are balanced, resulting in no change in the object's motion.

There are two types of equilibrium:

* Static Equilibrium: The object is at rest and remains at rest.

* Dynamic Equilibrium: The object is moving at a constant velocity (same speed and direction) and continues to do so.

Example: Imagine a book sitting on a table. The force of gravity pulls the book down, but the table exerts an equal and opposite force upwards, preventing the book from falling. The forces are balanced, resulting in static equilibrium.

Let me know if you'd like more examples or details!