WHAT IS TOK PISIN?

Tok Pisin (pronounced /tɔːk pɪzɪn/ in English, locally pronounced [tokpisin]) is a creole spoken throughout Papua New Guinea; in parts of Western, Gulf, Central, Oro Province and Milne Bay Provinces the use of Tok Pisin has a shorter history, and is less universal, especially among older people. It is an official language of Papua New Guinea and the most widely used language in that country. Pidgin spoken in Papua New Guinea, hence its identification in some earlier works as New Guinea Pidgin. It is a form of Melanesian Pidgin English that was developed in the early 1800's as a result of increased travel and economic activity between the Melanesians and Europeans. It was also once called Neo-Melanesian, apparently according to the hypothesis that all English-based Melanesian pidgins developed from the same proto-pidgin. It is one of the three official languages of Papua New Guinea, along with English and Hiri Motu. Tok Pisin (literally, “talk pidgin”) is one of the Pacific pidgins that emerged during the second half of the 19th century on copra and sugarcane plantations to which labour was imported from Melanesia, Malaysia, and China. The extensive multilingualism that resulted called for a lingua franca. People who had traveled to Papua New Guinea from plantations in Samoa and Queensland, Austl., resorted to the pidgin that had developed there, as apparently did those from coastal China.
Between 5 and 6 million people use Tok Pisin to some degree, although by no means all of these speak it well. Between 1 and 2 million are exposed to it as a first language, in particular the children of parents or grandparents originally speaking different vernaculars (say, a mother from Madang and a father from Rabaul). Urban families in particular, and those of police and defence force members, often communicate between themselves in Tok Pisin, either never gaining fluency in a vernacular ("tok ples"), or learning a vernacular as a second (or third) language, after Tok Pisin (and possibly English). Perhaps 1 million people now use Tok Pisin as a primary language.
Tok Pisin is also—perhaps more commonly in English—called New Guinea Pidgin and, largely in academic contexts, Melanesian Pidgin English or Neo-Melanesian. Given that Papua New Guinean anglophones almost invariably refer to Tok Pisin as Pidgin when speaking English (and note that the published court reports of Papua New Guinea refer to it as "Pidgin": see for example Schubert v The State [1979] PNGLR 66) it may be considered something of an affectation to call it Tok Pisin, much like referring to German and French as Deutsch and français in English. However, Tok Pisin is favoured by many professional linguists to avoid spreading the misconception that Tok Pisin is still a pidgin language; although it was originally a pidgin, Tok Pisin is now considered a distinct language in its own right because it is a first language for some people and not merely a lingua franca to facilitate communication with speakers of other languages.
Nearly the same grammatical distinctions are made in other Melanesian pidgins, such as Bislama (Vanuatu). These features constitute some of the clearest evidence that pidgin systems are not necessarily simpler than those of the languages from which they derived most of their vocabularies and that influence from the languages previously spoken by those who developed the systems (substrates) is incontrovertible in these cases. Such substrate influence is evident also in the sound system of Tok Pisin, where English /f/ has been replaced by /p/ and /š/ by /s/, as in pinis ‘finish.’Tok Pisin is considered an expanded pidgin, as complex as a creole, as it is spoken in urban settings as a vernacular rather than as an occasional lingua franca. The nature and theoretical foundation of the distinction between an expanded pidgin and a creol is an issue of current debate among linguists.

Source:
http://www.britannica.com/EBchecked/topic/598181/Tok-Pisin
http://www.answers.com/topic/tok-pisin