depends... you can dowload games (you should own them if you download them wink wink), you can try homebrew apps (or games) and surely more (I haven't really used my wii u that much, only 3ds)

i modded my vwii after following the guide

if you own any other game for another console (you need to own it it wont work if you dont own it) you can inject it onto yrmenu

you can download NUSspli but you are only allowed to download games if you own them (bcs then it's illegal if you don't own the game) you'll also need sigpatches to run them (it's in the HB appstore)