Fear is a very strong feeling that all humans and many animal species know. You feel fear when you feel threatened. This can be a dangerous animal, a strong thunderstorm, a car speeding towards you and many other things. We then also say: we are afraid of these things.
But you can also be afraid when you are simply in a situation where something bad could happen. If you have to cross a dark tunnel, there might not be anything threatening yet. But you suspect: something could happen.
Most of the time it is very unpleasant to be afraid. When you are afraid, you feel strong changes in your body: you start sweating, your blood pressure rises, your breathing and heartbeat become faster and your pupils dilate. The muscles also tense up. Sometimes you feel nauseous or even pee your pants.
The body's reactions to fear have an important function: because they are unpleasant, you avoid dangerous situations. This protects you from danger. But if you are already facing danger, your body is on the alert: you can either flee quickly or you may even have to fight for your life. The body is then well prepared for both with its tension. This is how it has developed in humans and animals in the course of evolution.