Coming from someone who does not use Twitter and knows little about it, what do you think constitutes a 'public figure' in Twitter's view? Someone who can sell

Coming from someone who does not use Twitter and knows little about it, what do you think constitutes a 'public figure' in Twitter's view? Someone who can sell out an arena? Someone who writes a blog read by tens of thousands of people? A Youtuber with 2000 subscribers?