A hashtag is a symbol (#) that people put in front of words or phrases on social media. It's like a label for a post. It helps people find posts with similar topics. It's like when you organize your toys in different boxes so you can find them easily. For example, if you put #puppies in your Instagram post, people who search for #puppies will be able to find your post easily along with other posts with the same hashtag. Hashtags can be used for anything from a fun challenge to a serious social cause.