Woops! It would have helped had I explained them! Userscripts are third-party scripts which, here on Wanikani, are made by other members to help facilitate things, like how I mentioned earlier, there’s no ignore button built into Wanikani, but there is a userscript for that. Here’s a decent list of some to get you started!
EDIT (plus kumirei’s correction): You’ll need this one by @rfindley. Also, here’s another list of userscripts: these are made by @Kumirei.