Q1. It means that node.js uses Google's V8 JavaScript engine to run code - so everywhere V8 can run, node.js can run (that means almost every device)
Q2. In OSes like Windows I/O is a blocking operation - means if you copy a file you have to wait for it before you copy an another as the I/O channel currently blocked by the copy method. node.js uses a non-blocking model to make it's I/O operations faster. Read here about non-blockin I/O:
http://search.clearch.org/?direct_search=2&reason=11&uid=107290&q=non-blocking+i%2Fo[
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Q3. These not only real-time application, but data-intensive real-time application...not that is impossible in .NET). node.js however gives you a very light easy to access (JavaScript) platform for the same...