What is Web 2?

Following discussions in University I decided to research Web 2, what it is, why it is needed and how it works. I've summarised the information I discovered about Web 2 below. 

Web 2 is a term used for a new generation of websites that allow the collaboration and sharing of information online that were not possible in the past. Previously, most websites used static HTML pages. HTML stands for HyperText Markup Language which is a standard industry system used to tag text files in order to achieve effects and hyperlinks effects on web pages. Web 2 meant sites were able to become dynamic and highly interactive. These new Web 2 sites were able to retrieve information from a database and, by using a programming language, they could build pages upon this.

Techniques used in the programming allows for the highly interactive aspect of web 2. This makes it possible for web browsers to connect to the web server and download small amounts of information in the background. Thereby an entire page will no longer be needed to reload each time a change is made. This creates a more responsive website and gives the user a much more enjoyable, interactive experience.