well for me I can't say exactly. e.g. I don't really fear heights because planes and high buldings are ok. but the moment I'm in a high building and feel the wind on my skin, I feel like falling and begin to panic. same with leaning my back on the balcony or seeing how other peple do this while smoking. only thinking about it freaks me out.
That is acrophobia.
You see the problem is that there are no clear definitive definitions of those phobias. They're all interconnected and overlapping with each other, for example aviophobia although it is mainly fear of flying, it can also be associated with other phobias such as acrophobia and claustrophobia.