Etherpad Lite is a real-time collaborative text editor which allows multiple users to simultaneously fiddle with a document. Everyone can see everyone else’s changes in real time, which is really cool. The “lite” tag after the name is there because the Etherpad Lite project was spawned from the ashes of the original Etherpad project, which itself was snapped up by Google and transformed into the ill-fated Google Wave. Wave was never really all that popular and has since been killed, but the core idea is still totally cool—to present a document to more than one user and have all users be able to make changes to it, and to have those changes shown to all other users as they’re made. It’s a surprisingly complex problem to solve. For one thing, it’s entirely possible that more than one user can change the same thing at the same time; there has to be a way of telling who “wins” and whose changes are tossed out. Even more complex is figuring out a way to track all the changes and organize them, and then display them for everyone.