Hashtags are a type of metadata tag used on social network and across the internet which makes it easier for users to find messages with a specific theme or content.
Users create and use hashtags by placing the number sign or pound sign (colloquially known as the hash character # in reference to its resemblance to several slices or chops with a sharp implement) in front of a word or unspaced phrase, either in the main text of a message or at the end.
Searching for that hashtag will respond each message that has been tagged with it. A hashtag archive is consequently collected into a single stream under the same hashtag.For example, on the photo-sharing service Instagram, the hashtag #bluesky allows users to find all the posts that have been tagged using that hashtag.

The term hashtag can also refer to the hash symbol itself when used in the context of a hashtag.

Hashtag use is getting ever more popular and is now starting to be used to create fashions, start movements or gather people. They provide synergy across the internet to common causes and embrace the greatest elements of internet culture.