People develop phobias about many things like darkness, social situations, spiders, or blood.
Agoraphobia , one of the most common phobias, involves the fear of open places. A person with agoraphobia feels anxious in places where it would be hard to escape, like being in a crowd, standing in line, being on a bridge or traveling in a car. In extreme cases, they are so immobilized by fear that they become a prisoner in their own home. In some people, the response to a phobia can be fairly mild. For example, a person who has a phobia about flying might simply avoid airplanes.