I am always getting questions about what the hashtag sign, #, on Twitter really means. It’s good to know the answer because more and more Internet platforms have started using hashtags as well.

Definition: The # symbol, called a hashtag, is used to mark keywords or topics in a Tweet. Twitter users use it as a way to categorize messages.

The hashtag symbol # also makes the keywords readily searchable. Just click on a hashtagged word in any Twitter message and you will easily find all other Tweets marked with that keyword.

It’s as simple as that!

Now that you understand what the so-called mighty hashtag # stands for, watch the Jimmy Fallon and Justin Timberlake video above. It has been viewed 22 million times. You will never forget what a hashtag means again.