"What is the difference between Visual Basic 6 and Visual Basic .NET?" certainly ranks as a giant among other Frequently Asked Questions [FAQs] is
In short, Visual Basic .NET is based on the .NET Framework and its object architecture. It is quite distinct from historical VB, even Visual Basic 6.
As Dave Ranck wrote, responding to this question in 2002, "Because the .NET Framework is fully object-oriented, .NET languages also must support OOP (object-oriented programming) features. The result is that Visual Basic .NET is fully object-oriented. This is a huge difference and is a powerful improvement over previous version of VB. It also introduces another level of complexity along with this new power" -- complexity that Visual Basic 6 lacked.
For more, read How do VB6 and VB.NET compare?