With server-based data querying and tools designed to mine that information for HTML use, data is not only easier to get, but also it is formatted for use on any Web browser. Using a three-tier model, we have a client, a server and a data store. Since the client is simply a Web browser, data access development only happens on the server. Clients talk to the server, where they are authenticated and to which they submit requests. The server, if authentication warrants, passes the query to the data store, retrieves the proper information, formats it and sends it back to the user.
Development cycles are limited to server-based development.
In addition, code can be reused on the server. In the past, applications were standalone, client-side querying devices. Now the server holds all the logic, allowing modules to interoperate a nd to make more complex queries and decisions. You must contend with a few bandwidth issues here. In the old model, clients are very intelligent, requesting only data structures.