Google Docs predates Wave and has since been rebranded as Google Drive. Various blogs have pointed out how certain aspects of Wave have been integrated into Docs/Sheets/Drive. The big concept with wave was that you did operations. "Go to row 12 and bold characters 15 through 38" as an operation within a document, as opposed to synchronizing an entire object. So when you set your cursor on a word in the document, it sent that as an operation, and any other clients editing the document could see where your cursor was at. Operations at the individual character level would sync to all attached clients and you can see edits in realtime. It's really interesting when a team at work is all looking at and modifying the same spreadsheet. The box they are editing is highlighted so you naturally stay away from it. If you are "idle", you might click your cursor away from all the activity as a common courtesy.

Good Docs had this to a degree before Wave, but it was unpolished. Two people could definitely edit a sheet together, but editing a document was more cumbersome (whole blocks of text would update at once). After Wave, they took the concepts and you could then see everyone editing the document as they typed or simply moved around the document.