Layered Architecture is commonly using when design J2EE application - it is something like defacto standard and widely known by most architects, designers, and developers. The layered architecture pattern closely matches the traditional IT communication and organizational structures found in most companies, making it a natural choice for most business application development efforts. 

Layered Architecture Pattern

One of the powerful features of the layered architecture pattern is the separation of concerns among components. Components within a specific layer deal only with logic that pertains to that layer. Following is the example of 4-tier architecture. It can be simplified to 3-tier or 2-tier by the case.

4-Tier Architecture Pattern