Directly from the website: Agile Draw is a lightweight, expressive convention for modeling that promotes effective communication over tools and understanding over processes. The core of Agile Draw includes four components: circles, boxes, lines, and text; these indicate different aspects and relationships of the model. The Agile Draw extensions provide guidelines to make the models visually appealing. Agile Draw is meant to be useful in any drawing context, whether drawing by hand, or using a software application..
You might wonder if this is yet another attempt to take advantage of Agile as a buzzword or what. I'll leave to you the judgment :-)