What is difference between N-tier vs N-layer architecture ?

N-tier and n-layer are entirely different concepts. People often use this term interchangeably during the design of the application architecture. N-tier refers to the actual n system components of your application. For ex: Suppose you create a web application, its components include your application server where it is being hosted, the database being used with it, on another server and the user machine who access the application, forms the third component. These are referred to as the 3 tiers of your application. So they may be n in number and so the term n-tier application. So tiers are the physically separate components of the same system. On the other hand, layers refer to the internal architecture of your component. For ex: in your code, you divide the code into different layers like Data access layer, Business logic layer etc.. So they are internal to the component and these layers interact with each other internally to form the entire component.