Authentication is the process of scrutinizing the identities of users for the purpose of security. It is usually the first checkpoint when accessing a network or a device. This is done through a login process that requires the user to provide one or multiple forms authentication.
Types of authentication.
What-you-know is a common form of authentication. It only requires information as proof of identity; for example, a username and password, or a pin. If the information is stolen or shared, the account immediately becomes vulnerable.
What-you-have is a step towards a more secure form of authentication. It uses tangible objects, like, smart cards and tokens to provide a higher standard of security. What-you-have is more costly to implement on networks than what-you-know, but replication of the authentication objects is far more difficult.