Linguistically, "pidgin" is a 'makeshift' form of communication that has developed from two or more languages used by people who do not share a common language. Pidgins are not themselves a native language but evolve due to people with differing languages needing to communicate with each other. Imagine two people are shipwrecked on an island with one being an English speaker and the other speaking Russian.
In order to survive they would communicate with each other using their own language. After being on the island a few weeks before their rescue they would most likely develop a pidgin form of communication using words and elements from both English and Russian. Pidgins can evolve and develop into its own language that a group of people use as their native tongue. Once a pidgin is used as a native language it becomes known as a creole.