Multi-tier client-server architectural model CONSISTS of various components KNOWN as tiers that interact with each other. The below image represents the three-tier application model which has client/presentation tier, business logic tier and the database tier which interact with each other to process a request and send a response:

In the multi-tier system, we have the following advantages:

• Any changes to the user interface or business logic can be DONE independently.
• It introduces abstraction between the components. For example, the client tier can access data without knowing from where and how the response comes from, what is the server infrastructure available in the BACKEND etc.
• Each tier can be coded or developed independently. For example, the middle tier can be coded in Java or python, the client tier can be coded in Angular or REACT etc.
• The database can have pooled connections for sharing data among multiple users without the need for creating a new connection for every user.