1 It refers to the separation of the logic (i.e the code and design) that is developed for an application in different files. It refers to the physical location of the Layer files.
In an ASP.NET web site, we create GUI web forms, business logic , data access
logic, database all in one computer. In this case, we have 4 layers and 1 Tier.
if the GUI Web Forms,business logic, data access logic and database are all in
different computers, we have 4 layers and 4 Tiers.