Phobia is a derivative of the Greek word phobos, meaning fear. It does seem however, to have two different definitions. Here are a couple of examples: a) an extremely intense and overwhelming sense of fear with regard to a specific stimulus or b) an intense dislike or hatred of something.
Here are a couple of examples: Arachnophobia is an intense fear of spiders. I know a few people that have this particular phobia and I find it quite disturbing to watch just how they react upon sighting one. This reaction can even present itself when they view a picture of one or see one on TV. Its obvious that spiders cause them a great deal of discomfort.
Homophobia is a fear of homosexuals. Here we see a different interpretation of the word phobia. In this case it means an intense dislike or hatred toward homosexuals rather than an intense and overwhelming fear that would invoke terror in the heart of the homophobic.
So, what is the difference between a phobia and a fear? Most people have fears of one kind or another. Fears of: examinations, speaking in public, etc. etc. In fact, I have a fear of public speaking. A couple of times in my life, Ive been asked to stand up...