An SSH key is a secure access credential used in the SSH (Secure Shell) protocol, which allows users to connect to remote computers safely. It consists of a pair of cryptographic keys: a public key, which can be shared with anyone, and a private key, which must be kept secret. This key pair enables secure authentication without the need for passwords. When a user attempts to connect to a remote server, the server checks the provided public key against its stored keys. If there’s a match, the user is granted access. This method enhances security by reducing the risk of password theft.