According to the App Store description (and what we already knew), the app will facilitate voice chat, be home to dedicated game services like SplatNet2 for Splatoon 2, and help you connect with friends via the Nintendo Network and other social media websites. The app now doesn't do much, but it will support the online features of "Splatoon 2", which is scheduled to be released this Friday, July 21.
If you disconnect from online multiplayer matches in Splatoon 2 enough times, the game will give you a warning that you could be banned from playing online if you keep disconnecting. It's an nearly aggressively limited service, and this is before we get into the mess of cables you'll need if you're going to want to play online with headphones in the Switch's handheld mode - something which it would seem is only possible with a separate splitter available elsewhere.
Splatoon 2 is nothing if not charming.
The backbone of Nintendo's online features for the Switch is now available.
This app is, of course, free to download and available now on the App Store, but Nintendo's online services are only free until 2018. Graphically underpowered and aesthetically confused, the Wii U was such a flop that some analysts speculated it would mark the beginning of the end for Nintendo's time in the console business.
A lot of multiplayer-focused games don't have a single-player mode at all, so the fact that Splatoon 2's is a bit dry is barely a complaint. The most notable instance of the device's painfully old-fashioned ways is the Switch's approach to voice chat. Others are struck with this realization when they are playing their Switch and public and realize that they'll likely need to switch over to a phone or tablet to listen to music. Additionally, you can invite people to private battles, league battles, Salmon runs, and Splatfest battles.
We assume this message means that the servers aren't yet live, but that the app has been pre-released in advance of Splatoon 2's release on Friday. When your friend's made a room and invited you in, you'll get a notification.