In case you're not quite sure what Pig Latin is, you could read the wikipedia article on Pig Latin, otherwise I'll give a brief explanation here.
Pig Latin is not an actual language. It's what linguists call a "language game". A language game (also sometimes called a "ludling" or "argot") is a set of rules applied to an existing language which make that language incomprehensible to the untrained ear.
The rules used by Pig Latin are as follows:
Of course, Pig Latin is not a form of real Latin. It's only called that because it sounds like a foreign language when spoken. The word "pig" has less obvious origins. It may have originated from the term "dog Latin" which is sometimes used to describe poorly written or spoken Latin.
The origins of Pig Latin go can be traced back to at least 1886 where a preserved article make a reference to "hog latin" which is spoken by young children. It is believed that the modern version of Pig Latin was first described ina 1947 newspaper.
These three words are probably the most well known Pig Latin words. In some areas and cultures they have even managed to enter the common vocabulary. Below are the definitions of these words: