Even so, most people associate the term client with the physical computers they are using and the term server with some other physical computer to which they are connected. But first, there are some important things you should know about general software architecture.
Most application programs have three major layers.
The top layer is the presentation layer, which provides the user interface. The presentation layer handles input from the keyboard or mouse and outputs in the form of screen displays. In the middle is the application or business logic, the functionality that gives the application program its character. The bottom layer provides the generalized services needed by the other layers, including such things as file services, print services, communications services, and, perhaps most important, database services. A one-tier application is one in which the three program layers are tightly connected.