I don't understand posts like this one. The question is so broad that it indicates virtually no preparation by the student. Surely your text has a discussion of the subject, with examples.
If there's some part that's troubling you, like asymptotes, what it means to be undefined, etc., then we'll be glad to try and clarify. Otherwise, you're likely to get links to helpful web sites (see above), which you ought to have pursued on your own, before coming here looking for a knowledge dump.
If you're totally lost, review your text, do a web search, and if none of that helps, then come on back with a specific area of difficulty. There may be more than one -- that's ok, feel free to come on back again -- but don't expect essays here that cover entire topics.