What exactly is Dot Net? It's easiest to clarify by first saying what it is not. It is not a language. In fact, one of its beauties is that is allows the use of several languages seamlessly in the same application (for example, in a larger project there could be several programmers each using their own favorite language, but each interacting seamlessly with the others - maybe not a good idea to do, but it's great that you could!) The big advantage here is in the ability to reuse code from another application that may not have been written in your language of choice.Dot Net provides the means to overcome obstacles that have traditionally been in the way of the development of true web based applications (eg "Session State" - more later!).
Dot Net is a strategy for delivering applications over the Web as Web-based services. In the case of our earlier example, it would be possible to build a series of pages that provide all the functionality of the checkbook program, including the interaction with the bank's on-line system, and to offer this as a service delivered over the web. This is a form of the Application Service Provider model .Components of the .Net strategy include platforms (Microsoft's ".Net Servers") which include the .Net Framework (.Net's foundation infrastructure) and a set of programs or tools for developing and running .Net applications. Microsoft's latest Office products include features for .Net, and of course, there's Visual Studio.Net - the comprehensive integrated development environment. There are new languages to use in your development, including Visual Basic.Net, C# (pronounced "C Sharp"), the Java like J# and others. Some of these are distributed along with Visual Studio.net.