What do you mean by normal reaction?

Explanation

### Step-by-Step Solution:

1. **Understanding Normal Reaction**:
The normal reaction, often referred to as the normal force, is a force exerted by a surface that supports the weight of an object resting on it. It acts perpendicular to the surface.

2. **Application of Newton's Third Law**:
According to Newton's third law of motion, every action has an equal and opposite reaction. This principle is crucial in understanding the normal reaction.

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