I'm not a linguistics major, but I can be a little more specific. Pidgins are languages that traders & natives make up for business purposes -- typically, the traders' vocabulary with the natives' phonetics & syntax. Indeed, "pidgin" is pidgin for "business", in the Pacific pidgin spoken by Chinese-speaking coolies & English-speaking traders. Being a business language, a pidgin has a restricted vocabulary, confined to what is useful for making deals & giving orders. But if a country is flooded with imported laborers speaking different languages, the pidgin is the only language they have in common, so the children flesh it out into a complete language, and that's a creole. It happened in a lot of places -- Haiti & Hawaii come to mind.