Hashtags are a way of 'tagging' or 'labelling' an update or tweet with a specific keyword relating to the topic of the update. Users can then click on the hashtag link to show all updates and tweets talking about the same topic. Hashtags are well supported on Twitter, Google+, Instagram and LinkedIn, so you could say Facebook have been a little slow on the uptake, but they're finally here!
Facebook is now including hashtag support and will hyperlink all words that begin with a '#' in status updates.
What this means for users
Users will be able to search for certain hashtags by entering '#' before the search query, or click on hashtags within updates to see other updates containing the same hashtag. Pages and people that are not directly connected, i.e. people they are not firends with or business pages they have not 'liked', may show up in these results.
What this means for businesses
Adding hashtags to your updates can increase the reach of your updates. Your updates can now be shown to users searching for specific hashtags that wouldn't normally see your messages, increasing your potential audience (if used correctly!).
What Facebook say
"Hashtags are just the first step to help people more easily discover what others are saying about a specific topic and participate in public conversations.
"We'll continue to roll out more features in the coming weeks and months, including trending hashtags and deeper insights, that help people discover more of the world's conversations."
Source: BBC News