Networking - Application Layer Interview Questions

What is application layer? - The application layer is located at the top of the TCP/IP protocol layers.........
Define DNS - The DNS translates Internet domain and host names to IP addresses.......
Define Telnet - Telnet is the main Internet protocol for creating a connection to a remote server..........
Define SMTP - SMTP - Short for Simple Mail Transfer Protocol, a protocol for sending e-mail messages between servers.........