http://www.nintendo.com/switch/online-service/
Free until 2018
"This paid service lets Nintendo Switch owners enjoy online multiplayer gaming as well as a dedicated smartphone app that connects to your Nintendo Switch system and helps you connect with friends for online play sessions."
"Online Play on Nintendo Switch
You'll be able to play compatible co-op and competitive games online by signing in with your Nintendo Account. Online play will be free for Nintendo Account holders until our paid online service launches in 2018. "
"After the free-trial period, most games will require a paid online service subscription from Nintendo in order to play online.
This service is only for Nintendo Switch. It does not affect online play or features for the Wii U or Nintendo 3DS family of systems."
"Online lobby and voice chat
Our new dedicated smart device app will connect to Nintendo Switch and let you invite friends to play online, set play appointments, and chat with friends during online matches in compatible games─all from your smart device.
A free, limited version of this app will be available for download in summer 2017.
Classic Game Selection*
Subscribers will get to download a compilation of classic titles with added online play, such as Super Mario Bros. 3, Balloon Fight and Dr. Mario."
Update
Netflix style VC
https://twitter.com/jasonschreier/status/870458277724860421
"Nintendo confirms to Kotaku that monthly classic games are NOT happening. Replaced with a way better service: "
Free until 2018
"This paid service lets Nintendo Switch owners enjoy online multiplayer gaming as well as a dedicated smartphone app that connects to your Nintendo Switch system and helps you connect with friends for online play sessions."
"Online Play on Nintendo Switch
You'll be able to play compatible co-op and competitive games online by signing in with your Nintendo Account. Online play will be free for Nintendo Account holders until our paid online service launches in 2018. "
"After the free-trial period, most games will require a paid online service subscription from Nintendo in order to play online.
This service is only for Nintendo Switch. It does not affect online play or features for the Wii U or Nintendo 3DS family of systems."
"Online lobby and voice chat
Our new dedicated smart device app will connect to Nintendo Switch and let you invite friends to play online, set play appointments, and chat with friends during online matches in compatible games─all from your smart device.
A free, limited version of this app will be available for download in summer 2017.
Classic Game Selection*
Subscribers will get to download a compilation of classic titles with added online play, such as Super Mario Bros. 3, Balloon Fight and Dr. Mario."
Update
Netflix style VC
https://twitter.com/jasonschreier/status/870458277724860421
"Nintendo confirms to Kotaku that monthly classic games are NOT happening. Replaced with a way better service: "