Engine Yard created an infographic that will help you learn about node.js:

"Node.js is a server-side framework for JavaScript that has experienced explosive growth over the last couple of years. When it first started gaining momentum in the developer community, it was hailed as “the new Rails,” and after surpassing Rails on GitHub as the most-starred repository, some even referred to it as “the new PHP.” Comparisons aside, while there isn’t just one right language or framework for building apps, Node.js certainly is a suitable framework for building a particular kind of app; Node.js is the go-to development framework for making event-driven, low-latency, concurrent apps. Yet despite its popularity, Node.js is still in its infancy..."

Courtesy of: Engine Yard