n-tier is ambiguous imo, but its usual definition refers to partitioning
your application into multiple physical tiers (think distributed
application). This could be as simple as a winform client, with a
database server, and some of the logic being leveraged from web services
on one or more web servers. You could take it a step further by saying
for instance that security services are provided by your active directory.

I think that what you are describing is better referred to as a layered
application, which can be achieved without involving other "tiers".

Regards,

John Parrish

Thus wrote Vascas,

Tiers refer to physical processing nodes. Your application is probably 3
layered (which is good), but not 3 tiered (which doesn't mean it's bad).

Cheers,