What is the Web 2.0?

I often ask this question to people, and I've come to expect a wide array of answers. Last week I got one that may actually stand the test of time (we tend to re-define things in this industry).

Web 2.0 may very well be a service mark (https://www.theregister.co.uk/2006/05/26/web_2point0_battle/) owned by O'Rielly Media. Whoa.