Most web applications are built in a three-tier architecture that consists of three important layers: data, logic, and presentation. In web applications, the application structure usually breaks down to database, server, and client, while in modern web development, it can also be broken into database, server logic, client logic, and client UI.

A popular paradigm for implementing this model is the Model-View-Controller (MVC) architectural pattern. In the MVC paradigm, the logic, data, and visualization are separated into three types of object, each handling its own tasks. The View handles the visual part, taking care of user interaction. The Controller responds to system and user events, commanding the Model and View to change appropriately. The Model handles data manipulation, responding to requests for information or changing its state according to the Controller's instructions. A simple visual representation of the MVC architecture is shown in the following diagram:

Common MVC architecture communication

In the 25 years of web development, many technology stacks became popular for building three-tier web applications. Among those now ubiquitous stacks, you can find the LAMP stack, the .NET stack, and a rich variety of other frameworks and tools. The main problem with these stacks is that each tier demands a knowledge base that usually exceeds the abilities of a single developer, making teams bigger than they should be, less productive, and exposed to unexpected risks.