Lil Nas X’s “Old Town Road,” the meme turned song of the summer, has been the number-one song in country for a record-breaking 17 weeks. It originally took off on TikTok, a video-sharing app you should really be paying attention to. It’s been downloaded a billion times, and Facebook execs flagged it as competition during recent Congressional testimony. It’s also owned by a Chinese company, Bytedance, that was just hit by FTC fines for collecting children’s data. This week, The Wall Street Journal’s Georgia Wells catches us up on everything we need to know about the favorite app of every kid these days.