N-Tiered vs N-Layered architecture/design

Question

What does it mean by N-Tiered and N-Layered architecture/design?

Is there any difference between N-Tiered and N-Layered architecture/design?

If yes, what is the difference?

Answer 1

N-tiered refers to the "distributed" layers of a system (i.e. server and client), whereas n-layered refers to the layers in a self-contained program; although the two are often used interchangeably, some suggest that there is a significant difference (like the one I mentioned above), as seen on the first paragraphs on Multitier architecture and Multilayered architecture on Wikipedia explains the difference.

Answer 2

People often use the two terms interchangably in that they can describe an architecture as being both multi-layered and multi-tiered. My take on it is that generally a tier refers to some physical separation while a layer is more of a logical separation.

For example, a typical web application I would say has a front end - what's displayed in the browser - and the actual application logic running on the application server, and a database. This could be referred to as 3 tiered, since there is a database server, an application server and the client machine. Just as easily, however, one may refer to the database layer, the logic layer and the presentation (or UI) layer.