What is Web 2?

I have just started thing 2 and reading through have been exposed to many things that i didn't know exist, so left feeling a little overwhelmed.So one of my goals of being aware of whats on the web to make use of is already being addressed. i had no idea of the way health care was using information so easily w/MDs and that one could subscribe to organize web information. It will take me awhile to go through the opportunities. I really liked the list of web 2 examples and put that on my favorites to explore; briefly visited three sites that i want to return to. So that is another goal, to sample the opportunities and decide on several that i like and can use. For my personal life, i will use the google blog searches, esp for knitting.