D3 was developed at Stanford and was the successor to Protovis.
The main technical aspects of D3 include selections, transitions, and data binding. I will not be covering transitions here since that is a more advanced aspect of D3 and is not crucial to implementation. If you would like to learn more about transitions, this is a great resource.
There are built in methods for parsing JSON, CSV, text, html, tsv, and xml.
To use D3, it should be included in your page with this link. Updates are posted to the website when a new version comes out, but the old ones remain available.