An application server is a software engine that delivers 
applications to client computers or devices, typically 
through the Internet and using the HyperText Transfer 
Protocol. Application servers are distinguished from web 
servers by the extensive use of server-side dynamic content 
and frequent integration with database engines.

An application server handles most, if not all, of the 
business logic and data access of the application (a.k.a. 
centralization). The main benefit of an application server 
is the ease of application development, since applications 
need not be programmed; instead, they are assembled from 
building blocks provided by the application server