I believe that the user's browser would technically be considered the client application.

And if you want a Web database, TYPICALLY what would happen is that a database such as Access (basically just consisting of tables) would be put on the Web.

Then "dynamic" Web pages such as ASP or PHP pages would be created acting like the old desktop database's queries, forms, and reports to access the database - all hosted on a Web Server.

And a nice thing about all this is that if you need to make a change to the data or the application it can all be done on the server as opposed to going around making sure that all the users have the latest version of your software on their PC's...