I'm new in this field though having knowledge of OOP and Java. I want to know what the .NET platform is -- how...
does it differ from Java? Can Visual Basic be used for Internet programming? The .NET platform is an enirely new way to program for the Windows platform. It is fully object-oriented and allows many different languages to be used, such as VB.NET, C#, C++, Java and *many* more. The .NET platform or actually the framework, provides the base services needed to interact with the operating system. All languages use this framework and its objects. Therefore, no matter what language used, the undelying framework is exactly the same.
.NET differs from Java in that it allows multiple languages to be used, while in Java or J2EE there is only one choice: Java (but it is a very good choice!). Java allows you to run your Java code on any platform for which a JVM exists (at least in theory - in practice there is sometimes a bit of tweaking needed, especially when programming to application servers such as WebLogic). There is a 3rd party effort in full swing to port .NET to Linux and there will probably be more in the future. That would remove that distinction between the 2 platforms.
At the language level, C# and Java are quite similar. Both are derived from C and show it. Both have similar goals in mind such as the keeping things simple through removal of features such as pointers. A Java programmer should have little trouble getting used to the C# language. The great difference is in the framework and the Java SDK.
All .NET lnaguages are created equal. VB or C# or Pascal or COBOL or Eifel or any language can be used to do anything in .NET, including Internet programming. You can even create an object in say, VB and then derive from that object in C#! That's cross-language inheritance and its quite cool - although it should be used with caution so as not to complicate things too much.
If you are a Java programmer, I would think that using C# would be the easiest way for you to get started. It will feel more natural in programming OO than does VB. There are many good resources out there on learning the .NET platform, some of my favorites can be found here.