Nowadays they are all over to make you searching and tagging easier. #Hashtags.
A hashtag is a word or a phrase prefixed with the symbol #
“It is a form of metadata tag. Short messages on microblogging and social networking services such as Facebook, Twitter or Instagram may be tagged by putting “#” before important words, either as they appear in a sentence or appended to it.” is what Wikipedia says.
Twitter says in it’s Definition of Hashtags:
The # symbol, called a hashtag, is used to mark keywords or topics in a Tweet. It was created organically by Twitter users as a way to categorize messages.
Facebook is using Hashtags since a while and there is an interesting article titled “Everything you Need to Know About #Hashtags on Facebook”
Search by Hashtag
See an Infographic
My Thank you for this Infograpphic goes to Offerpop
Do you use Hashtags? If so, which one?