Take all the rich client features of your popular messenger platform (Facebook, Whatsapp, Snapchat, etc) weld them on-top of an IRC-like protocol to enable 'roo

Take all the rich client features of your popular messenger platform (Facebook, Whatsapp, Snapchat, etc) weld them on-top of an IRC-like protocol to enable 'rooms' and you have Slack. It's not a new or clever idea, but their marketing efforts have been brilliant. To such an extent in fact, that there are now a bunch of Slack clones out there all trying to do the same, complete with the same sort of interface.