An application server is a server program in a computer in a distributed network that provides the business logic for an application program.

The application server can be seen as a three tiered application one containing the UI User Interface part, the second one contains the business logic BI and the last one containing the data part.

• A first-tier, front-end, Web browser-based graphical user interface, usually at a personal computer or workstation

• A middle-tier business logic application or set of applications, possibly on a local area network or intranet server

• A third-tier, back-end, database and transaction server, sometimes on a mainframe or large server

Application server acts like a bridge between the database or data repository and the client who made the request in the network to the server.

Application server will get the data from the database server if needed then perform manipulation over it and then will return the result based on that manipulation.

Application server can be considered as an application logic in technical terms or it can be considered as a interface between the data and the user in layman terms.

All the decision making process we call it as DSS will be done with the help of the application server in the network.