Things that are currently popular and being talked about a lot on social media and even in person. It's a way to link conversations and ideas together, too. Well, the hashtag linking part. So you go to a hashtag on your phone or computer on Twitter or Facebook and when you use # and put words after it, it creates a link to bind all similar topics together for easy search. Theoretically it would work the same here. People would tag their posts with #blamenickfury or #multiversedisplacement or basically anything you wanted, and you could see them all. When the hashtag is used a lot, it's popular, which makes it a trend, which means it's trending.