Does the sight of a snake fill you with panic and the desire to run away as quickly as possible? If so, you have a fear of snakes.
People have fear for many things: bugs, guns, heights, etc. Horror movies try to fill the audience with fear. Some fears make more sense than others. The fear of jumping out of planes makes a lot of sense, but the fear of public speaking isn't as logical: it won't kill you. Fear includes anxiety and can be very emotionally painful. If you're scared of anything, you know what fear is all about.