A multilayered software architecture is using different layers for allocating the responsibilities of an application.
There is also an architectural pattern that is named Layers and has been described in different publications, including the book Pattern-Oriented Software Architecture A System of Patterns. [1]
The concepts of layer and tier are often used interchangeably. However, one fairly common point of view is that there is indeed a difference, and that a layer is a logical structuring mechanism for the elements that make up your software solution, while a tier is a physical structuring mechanism for the system infrastructure. [2]