I have been developing apps for many years using multi-tier (or multi-layer) architectures, that is, Presentation Layer, Business Object Layer, and Data Access Layer. The 'normal' stuff.
However, I hear more and more people talking about 3-Tier or n-Tier apps.
My understanding is that Tier is physical (deployment) and Layer is conceptual (how code is organized), but which is which?
When is it proper to use the word Layer and when the word Tier?
Thanks for your feedback.