23.2. Component Jargon
Component-based programming is sometimes shrouded in a fog of specialized jargon. Understanding these terms helps sort out exactly what a component is supposed to do, and it also allows you to understand MSDN articles about application design. If you're already familiar with the fundamentals of components, feel free to skip ahead.
23.2.1. Three-Tier Design
The idea of three-tier design is that the functionality of most complete applications can be divided into three main levels (see Figure 23-1). The first level is the user interface (or presentation tier), which displays controls and receives and validates user input. All the event handlers in your web page are in this first level. The second level is the business tier, ...