A latest technology to the old-fashioned LAMP/WAMP stack for building professional websites and real-time applications is MEAN stack (MongoDB, Express, AngularJS, Node.js), which is an open-source software.
Compared to traditional web-serving techniques where each connection (request) generate a new thread, taking up system RAM and eventually maxing-out at the amount of RAM available, Node.js operates on a single-thread, using non-blocking I/O calls, allowing it to support tens of thousands of concurrent connections (held in the event loop). Additionally, it is all based on the open web stack (HTML,CSS and JS) running over the standard port 80. In simple, it is really scalable.
It is very important to think that Node.js is especially suited for applications that require persistent connection from the browser back to the server such as chat programs, interactive games, real-time applications etc. If one is just building an application that does not necessarily need user/server COMMUNICATION, developing with other frameworks would be just fine and will take much less time. Node.js is well suited for applications that have a lot of concurrent connections and each request only needs very few CPU cycles, because the event loop (with all the other clients) is blocked during execution of a function.
With Express, you can still handle server-side routing and page generation, but the emphasis is now on client-side views, courtesy of AngularJS. This change involves more than simply shifting your Model-View-Controller (MVC) artifacts from the server to the client. And perhaps most important, you’ll move from a page-centric view of your application to one that is component-oriented. MEAN stack isn’t mobile-centric. AngularJS runs equally well on desktops and laptops, smartphones and tablets, and even smart TVs. And as the MEAN stack is growing in adoption, a variety of testing strategies have developed and available. With world-class testing frameworks such as MochaJS, JasmineJS, and KarmaJS, you can write thorough, comprehensive test suites for your MEAN app.
The single-threaded event-driven system is fast and simple, compared to traditional Java or ROR frameworks, when handling lots of requests at once. Knowing more about MEAN stack helps you to play around with the technology!