Kerberos is a type of Network authentication protocol, which uses a secret key cryptography to communicate between the client and the server. It was developed at MIT to mitigate many security problems like replay attacks and spying. It makes use of tickets to provide authentication for the server-side resources. It followed the idea of avoiding additional logins (single sign on) and storing the passwords at a centralized location.
In a nutshell, the authentication server, the ticket granting server and the host machine act as the leading cast in the process of authentication.