D3 on GitHub

Shamelessly copy and pasted:

"D3.js is a JavaScript library for manipulating documents based on data. D3 helps you bring data to life using HTML, SVG and CSS. D3’s emphasis on web standards gives you the full capabilities of modern browsers without tying yourself to a proprietary framework, combining powerful visualization components and a data-driven approach to DOM manipulation."

I really like the ideas but I am not sure I understand the terms :-(

Do I really understand what a JavaScript library is?
Well in the context of D3.js, I guess it a set of JavaScripts that will do particular things. Somehow integrating HTML, SVG and CSS. Hopefully doing some of the work for us....