A testnet is an alternative or an instance of a blockchain that can be used for testing purposes and exists separately from the mainnet or main network. A blockchain testnet can support its native crypto assets, but these will have no intrinsic value as they cannot be used outside the test environment.
The blockchain testnet offers a secure and convenient platform where developers can deploy test projects and optimize them before launching them on the mainnet, where public users can access them. A testnet offers a limited and controlled environment for experimenting with and improving the code for developers before launching their applications or projects live.
A testnet is a simulation environment to experiment with blockchain projects, adding new features and subjecting them to testing. It is safer to identify and rectify potential issues in the code before launching a project to a live audience.