Turnkey is a product or service that is designed, supplied, built, or installed fully complete and ready to operate. The term implies that the end user just has to turn a key and start using the product or service. ... The turnkey becomes a trainer who turns the keys (of knowledge) over to someone else.
Turnkey refers to something that is ready for immediate use, generally. "Turnkey" is commonly used in the construction industry.
This term may be used to advertise the sale of an established business, including all the equipment necessary to run it, or by a business-to-business supplier providing complete packages for business start-up.