A multilayered software architecture is using different layers

Layer (object-oriented design)

In object-oriented design, a layer is a group of classes that have the same set of link-time module dependencies to other modules. In other words, a layer is a group of reusable components that are reusable in similar circumstances...

 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.

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.

See also

• Common layers in an information system logical architecture
  Common layers in an information system logical architecture
  The following four layers are the most common layers in a logical multilayered architecture for an information system with an object-oriented design:* User Interface Layer...
  
  
• Multitier architecture
  Multitier architecture
  In software engineering, multi-tier architecture is a client–server architecture in which the presentation, the application processing, and the data management are logically separate processes. For example, an application that uses middleware to service data requests between a user and a database...
  
  
• Shearing layers
  Shearing layers
  Shearing layers is a concept coined by architect Frank Duffy which was later elaborated by Stewart Brand in his book How Buildings Learn: What Happens After They’re Built , and refers to buildings as composed of several layers of change....