Nintendo had made it very clear that they will not be adding any more content to Super Mario Run, and that bug fixes and such would really be the only manner of updates Super Mario Run will get; this was actually a major point of contention among many of the game’s detractors, who hold that the game has a paucity of content for the price it is asking.
It’s unclear whether the new update will change their minds, but it seems to be rather substantial- Friendly Run mode is a brand new multiplayer mode added to the game that lets you race through courses against friends. Like with Toad Rally mode, the multiplayer here is asynchronous and passive, and like with that mode, the game requires a ticket. It also requires you to have added at least one person to your friends list in game.
So, it sounds like it’s a fun way to brag about your best times per course- assuming you are able to put your best foot forward in Friendly Run at all. Time to start practicing on those courses in single player first!