Node.js uses asynchronous programming!
A common task for a web server can be to open a file on the server and return the content to the client.
Here is how PHP or ASP handles a file request:
Here is how Node.js handles a file request:
Node.js eliminates the waiting, and simply continues with the next request.
Node.js runs single-threaded, non-blocking, asynchronously programming, which is very memory efficient.