The term "web 2.0" is jargon oftentimes utilized as a referential term pointing to the more recent wave of new ideas and concepts online. It is much along the lines of the "information age" being a blanket term for the age of internet technology and information sharing.
With this prevalence of information and increased competition for our online attention, websites must constantly strive to provide services or experiences that make things easier and more enjoyable for us, the common internet user.
There was once a time when people thought that huge technological inventions would constantly change the face of humanity. While this is true in many respects, over the last 1-2 decades the technologies that have really impacted our lives have not been groundbreakingly new, but have instead been efforts of lateral thinking. That is, they have been new uses for already-existing technology.
A fantastic example is Apple's venerable iPod. It's a cliche example, I know, but look at the phenomenon