What is meant by 3-tier architecture in web development, and what are the three tiersinvolved?

3-tier architecture in web development is a design model that separates the entire application into three interconnected layers or tiers. This separation allows developers to modify or add to one tier without affecting or needing to rewrite the entire application. It also enhances the security of the application as the client cannot directly access the database.

The three tiers involved in this architecture are:

1. Presentation Tier: This is the topmost level of the application and the one that users interact with directly. It can be a web page, a desktop UI, or a mobile app. This tier is responsible for presenting the data to the user and also interpreting the user's commands.

2. Application Tier (Business Logic Tier): This is the middle tier that contains the business logic, which controls how data is processed and managed. It acts as a mediator for data between the presentation tier and the data tier. This tier is where all the functions that need to be performed on the data are implemented.

3. Data Tier: This is the bottom tier that consists of the database servers. It's where data is stored and retrieved. This tier keeps data neutral and independent of application servers or business logic. It's responsible for storing and retrieving data from databases.

In summary, the 3-tier architecture in web development provides a model for developers to create a flexible and reusable application by segregating the application into different tiers.