Pig Latin is a constructed language game in which words in English are altered according to a simple set of rules. Pig Latin takes the first consonant (or consonant cluster) of an English word, moves it to the end of the word and suffixes an ay (IPA [eɪ]). For example, pig yields igpay, banana yields ananabay, and trash yields ashtray or rashtay (dependent on location/preferences).
The objective is to conceal the meaning of the words from others not familiar with the rules. The reference to Latin is a deliberatemisnomer, as it is simply a form of jargon, used only for its English connotations as a strange and foreign-sounding language.
More info: How to speak Pig Latin