Waht is the difference between Terminal server and Application server?

Answer 1

Today they are used interchangeably.

Historically, the terminal server was used to permit devices which had no network connections (ie console ports of various devices) access to a network via telnet or other connection. Application servers provided the same, but instead of a console connection, you were running an Application on someone else's machine.

Today, a terminal server provides a GUI session on a remote computer - and thus blurs the differences.

The usual reason for using an Application Server (sometimes via terminal services) is to ensure there are a limited number of users by license, or to provide access to a special set of hardware (cpu, array processors, etc) which may otherwise not be installed on each desktop.

Answer 2

They can be distinguished by what is expected as their client on the other side of network, a terminal server on a thin client app server on a fat client.

A connection from a terminal server had all its computing done on the server expecting the client does nothing but blitz the text or GUI pixels (this is in contrast to previous definition; here a GUI can be terminal server too)

While a connection from an app server expect that there is some computing capability of a full computer; fat client on the other side.

Terminals of telnet, X Windowing, Microsoft Windows types are common to college settings.