A database-driven web site is often using a three-tiered client-server architecture, which consists of three layers:
User Interface
It runs on a PC or workstation (the client) and uses a standard graphical user interface (GUI), which is usually implemented by using (X)HTML and CSS.
Functional Module
This level actually processes data.
It may consist of one or more separate modules running on a workstation or application server.
This tier may be multi-tiered itself.
The programming languages used for this module are usually with embedded SQL such as JDBC and PHP.
Database Management System (DBMS)
A DBMS is software that manages databases and allows users to access the data in the databases.
Two of DBMSs are Oracle and MySQL.
The major advantage of three-tier design over one/two -tier design is the added modularity makes it easier to modify or replace one tier without affecting the other tiers.