What Application is

Used interchangeably with program and software, this is a general term for a program that performs specific tasks, such as word processing, database management, e-mail sending or retrieval, or Web browsing. Unlike system software, which maintains and organizes the computer system (such as the operating system), an app is an end-user program.

The meaning of Server

A host computer on a network. It houses information and responds to requests for information (for example, it houses Web sites and executes their links to other Web sites). The term "server" also refers to the software that makes the act of "serving information" possible. Commerce servers, for example, use software to run the main functions of an e-commerce Web site, such as product display, online ordering, and inventory management (you'll also hear this described as shopping cart technology). A server is the control computer on a LAN, meaning it controls the software, access to printers, and other parts of the network (usually accompanied by workstations that "share the load"). A server may be dedicated (where its sole purpose is to be the server) or non-dedicated (where in addition to being the server, it can be used for basic computing purposes).