From Business Wire:
Wii is the best-selling system of this generation with more than 100 million units sold globally. Wii mini is for those who don’t own a Wii console and want to enjoy a ton of great Wii games on a stylish system at an affordable price. It is also for families who want an additional console in another room, allowing siblings and friends to play while the rest of the family enjoys other entertainment and games on the main living room TV screen. While Wii mini is not compatible with the Internet and will not allow online functionality when playing games, select multiplayer games can still be played locally with friends and families, which is the ideal way to enjoy such entertaining games like Super Smash Bros. Brawl and Mario Kart Wii.
This is an odd duck. As you may recall, the Wii U is selling poorly (though admittedly better these days), and part of the blame can be placed on the poor marketing choices made by Nintendo. When consumers have to be reminded that the Wii and Wii U are not the same thing, you've got a marketing problem. Adding a 'Wii mini' to the mix is not going to help matters. Nintendo should be focused on getting the Wii U on gamers' minds for the upcoming holiday season, especially with the impending arrivals of the PlayStation 4 and Xbox One.