Asp.Net 2 tier and 3 tier architecture ..

3 Tier Architecture:===================

1st Tier is your Presentation Tier which is your asp/aspx page.

2nd Tier is your Business/Logic Tier which is your custom components.

3rd Tier is your Data Tier which is your database MS SQL Server or Microsoft Access or ORACLE etc.


2 Tier Architecture:
===================
1st Tier is your Presentation Tier which is your asp/aspx page.

2nd Tier is your Business/Logic Tier which issues SQL statements directly to Database.

2 Tier Architecture eliminates the use of custom components, but its a good practice to use 3 Tier architecture to make secure your Business/Logic Tier.