What is it?
The layered architecture pattern is an abstraction representation of a system, where each layer represents a functionality. External layers represent visible and interface components and internal layers represent the back-end processing.
A layered architecture can have multiple layers, from simple systems with three layers to complex system with multiple ones. The most common way to represent layered architectures is to abstract into three layers, with user interface, business logic and database.
However, complex systems can isolate other components into other layers:
