Fear is an emotion much like anxiety. A person who fears something does not want it to happen, because they think something bad will happen to them if it does. Fear is the body's way of protecting itself from doing things that may be dangerous. For example, if one has a fear of jumping off a cliff, he/she will not do it. In this case, fear is a good thing but in others, it can be bad. An example of fear being bad is if it stops one from doing something important, like going to see a doctor.
Fear Facts for Kids. Kiddle Encyclopedia.