A phobia is an irrational fear of an object/situation that would not normally trouble most people. As the name suggests, simple/specific phobias are phobias that are about specific objects or situations. They can be quite distinct in nature and easily identified. For example, fear of spiders, fear of injections, fear of lifts or fear of heights.
Any phobia may produce a state of panic when the sufferer is confronted with the phobic object/situation. A wide variety of physical symptoms are experienced such as nausea, increased heartbeat and jelly legs. For this reason, many people with simple or specific phobias enter into a pattern of avoidance which can vary enormously in severity from someone who would not want to touch a spider, to someone who cannot even look at a picture of a spider in magazines, and therefore has to vet everything they come into contact with. The latter demonstrates just how debilitating a specific phobia can be.