A more thorough explanation:

Definition: Turnkey is an adjective used to describe a product that is ready to use immediately. It can also refer to a contract that includes everything needed to complete a project. As a noun, it refers to a jailer who is responsible for keeping the keys to a jail or prison.

• A turnkey computer network is a pre-built system that is ready to use right out of the box.
• A turnkey construction project includes all the necessary materials, labor, and equipment to complete the job.
• The turnkey jailer was responsible for keeping the keys to the cells and ensuring the safety of the inmates.

The examples illustrate how turnkey can refer to a product or service that is fully prepared and requires no additional work. In the case of the turnkey computer network and construction project, everything needed to complete the task is included, making it easy for the user to get started right away. The turnkey jailer example shows how the term can also refer to a person who has complete control over a specific area, in this case, the jail cells.