VB.net and C# are simply two different programming languages developed by microsoft. the underlying technology (.net framework) is the same, both are sharing the common libraries. here's an abstract from an article:

"C# is a JAVA-like language that borrows the good parts of Java and C/C++ and removes the bad parts. In the end, C#'s syntax is a lot like Java's. so if you're familiar with JScript, moving to C# will be easy enough. Ultimately, it is the .NET Framework of Classes that provides the functionality to perform tasks, while the languages themselves - VB.NET, C# etc. - are simply used to connect into it."

full article: http://www.4guysfromrolla.com/webtech/012702-1.shtml