Okay kiddo, an ATSC tuner is a little box that helps your TV pick up signals so you can watch your shows. You know how sometimes when you're watching TV, it goes fuzzy or looks like there's snow on the screen? That's because the TV signal isn't very strong. The ATSC tuner helps make the signal stronger so you can watch your shows without any fuzziness or snow. Think of it like a superhero who helps your TV get the best signal possible!