Difference between three tier vs. n-tier

Question

I just came across the following sentence:

As the industry has moved from a three tier model to n-tier models, the object relational impedance mismatch

Answer 1

The quote appears to be from this codeproject page. It also seems to do a pretty good job of explaining n-tier to include things like web services, javascript, workflows, etc. All things that 3-tier models don't necessarily include.