The adverb about, when used with a quantity, means approximately or roughly. If a teenager wants to have a couple of friends over, his mom might ask about how many "a couple" is — in his mind it may be about 50.
The adverb about can also be used for things that are almost, or just on the verge of happening. If you're about to graduate from high school, you're just finishing up your senior year. About also means around or on all sides. If you don't like animals, going to the petting zoo is a bad idea. The animals will be all about you.