Draft is a free, collaborative writing platform that provides a distraction-free environment. When you write in Draft you won't see anything but the text in front of you. Draft is stripped of options for messing about with font colors or inserting pictures.
Anyone who has an email address can participate in editing a document in Draft. Draft is a nice option for people who don't have access to Google Docs and or those who just want to focus on the text and not worry about playing around with font styling.