Web application is the application in which all or some parts of the software are downloaded from the Web every time it runs. Following is the explanation for each type:
Web applications may also run without the browser. A client program, which is either installed in the user's computer or on mobile device or is downloaded each session, interacts with a server on the Web using standard Web protocols. This is similar to the "client/server" architecture that prevailed in companies before the Internet exploded, except that today the server is on the Internet rather than the local network. Just like browser-based applications, the data may be stored remotely or locally. See rich client, cloud computing, ASP and SaaS.