What is the sign in with Coinbase API?

Could you elaborate on the significance and purpose of signing in with the Coinbase API? I understand that Coinbase is a leading digital currency exchange, but how does the API specifically handle authentication for users? Does it utilize traditional login credentials, such as a username and password? Or does it incorporate more secure authentication methods, like OAuth or API keys? Understanding the specifics of the sign-in process is crucial for developers and users alike to ensure secure access to Coinbase's services and functionalities.