Nintendo Network is a service from Nintendo that allows for the Nintendo Wii U and Nintendo 3DS consoles and some of their respective software to connect to the Internet. Launched as the successor to the Nintendo Wi-Fi Connection, it became public on January 26, 2012.
Compared to how Nintendo Wi-Fi Connection attempted to keep users anonymous and private, Nintendo Network uses an account-based system; in addition, Nintendo Network boasts multiple features previously not seen in Nintendo Wi-Fi Connection, such as the ability to patch released software.
In addition to these networking capabilities, Nintendo Network also covers the operations of Miiverse; in addition to allowing for the formation of communities, Masahiro Sakurai and other developers have notably used the service to showcase images of games currently in development.
In Super Smash Bros. 4
Super Smash Bros. 4 uses the service for its online multiplayer. A Nintendo Network account is also required in order to play the game online.
Due to advances in the Nintendo Network's infrastructure compared to the Nintendo Wi-Fi Connection, both the Wii U and 3DS versions of the game have received updates as to improve the base game.