The Nintendo Wii U was the 2012 follow-up to the hugely success Wii console. It took the idea of the Wii's family motion controls and added in a controller with a built in screen. Although this is seen as s commercially less successful (or to many gamers, a failed system), for families it has been hugely successful at offering ways of playing together still not possible on even never consoles like the Nintendo Switch that followed it.
Because the Wii U is a console that uniquely has two screens displaying different views of the game world it's excellent for games where players take on different roles. This was epitomised by the launch title Nintendo Land and extended with games like Affordable Space Adventure and Wii Party U. In these games one player uses the Wii U gamepad and screen with up to four other players use the classic Wii Remote controllers and the TV view. For families it can be quite magical.
The Wii U also has a strong library of big budget exhuberent games like Super Smash Bros. Brawl, The Wonderful 101 and of course The Legend of Zelda Breath Of The Wild which is visual as good as the Switch version of the game (the Wii U was the system it was originally design for).
The Wii U also has the benefit of being able to play many games on just the gamepad screen, freeing up the TV for other viewers. This turns the gamepad into a pseudo portable system and can even be used to play Wii games. Although it's worth noting that the range from the Wii U base isn't that great.
Finally, the Wii U fully supports all the Wii controllers and game discs. This opens the door to a huge library of games and greatly reduces the cost as purchasing a newer console with four controllers can almost double the price of a Switch, PlayStation 4 or Xbox One. Because of its reputation as a "failed" console you can regularly find Wii U consoles and games second hand at a really low price (£100/$120).