Application servers are servers that handle the processing of applications so the clients that connect to them don't have to. Thus you typically don't have to install the application on the client machine, the server does all the work, though you will likely need some type of interface with the app server, such as a web browser and in some cases a small piece of client software.
Typically application servers are web servers (coupled with database and other backend servers) that handle the processing of data based on web client interaction, like the servers that you log into when you want to look at your bank statement online. They are also OLTP servers that allow you to search a vendor's catalog for items, save your profile and/or account info and to make purchases.
See also Client-server
- Linux Application Server Environment (ASE) (www.sybase.com)