Some core concepts of Penflip to get you started:
The project page is the headquarters for you and your collaborators - you can write new content, edit existing content, invite collaborators, have discussions, browse changes, see project activity, export your project, and more.
You'll see 'Edit' buttons across the site. Clicking any of these buttons will take you into a distraction-free 'writing mode', similar to Google Docs and other writing tools. Everything is written with Markdown. For an explanation on why markdown is awesome for writing, read this.
Every project has a master version. Whenever you invite somebody to your project, a new version will automatically be created for them, and all of their changes will be made on their own version. When a collaborator is ready to submit their changes into the master version, they'll create a Merge Request.
A Merge Request is a group of changes to your project. All merge requests go into the master version. As the project owner, you control the merge requests: you can accept them, ignore them, and comment on them to suggest changes. When you accept a Merge Request, the master version of your project will be updated with those changes.
Still confused? Email email@example.com for help!