Earlier quoted context omitted.
To an approximation, the entire user interface and everything about how it worked. Edit: A more wordy response, since I assume the downvote implies that wasn't satisfying -- It has all the key elements - video chat, screen sharing, whiteboarding, etc., but they've all been arranged in such a different way that it's just impossible to single anything out in particular. The best I could do is explain it by analogy: Mos…
well, that doesn't tell anything.
IMO this is where UX often goes wrong, many people have a feeling for something but they don’t have the terminology to articulate it, nor the skills to reproduce it another context.