We can say these layers as a

• A presentation tier, for example a web app.

• An Business tier, including use case implementations and expose them such as a REST API.

• A data tier, such as a SQL database.

Other layers may include middleware, batch processing, and API. It’s important to note the layers are logical. Although they’re developed in isolation, they may all be deployed to the same target platform.

After learning the basics of N-Layer architecture, we should also understand the principles that we will apply on our architecture afterwards.

https://medium.com/design-microservices-architecture-with-patterns/layered-n-layer-architecture-e15ffdb7fa42