A hashtag is a type of metadata tag used on social network and microblogging services such as Twitter and Instagram. Hashtags make it easier for users to find messages with a specific theme or content. Users create and use hashtags by placing the pound sign (#) before a word or phrase in their post. The hashtag may contain letters, numbers, and underscores. The pound sign (#) denotes what is known as a "hashtag" on Twitter. This is simply a way to group tweets together so they are easily searchable by other users on the site. For example, if you were attending a concert, you might want to follow or search for the hashtag #concert to see tweets from other people who are at the same event.