"".NET is Microsoft’s answer to Java: it compiles
things into bytecode, it’s multi-platform, etc. Technically,
many argue that it’s “Java as it should have
been”. .NET isn’t free: while the virtual machine and
the language itself are ECMA standards, Microsoft’s GUI
libraries and other key components aren’t. This means
(surprise surprise) that you can’t write a .NET program for
Microsoft Windows, and run it under GNU/Linux, even though there is
a .NET virtual machine for GNU/Linux (called “Mono”).
If .NET is Microsoft’s answer to Java, Silverlight is
Microsoft’s answer to Flash. Silverlight allows you to run
.NET applications within your browser