Hashtags are a way to 'elbow your way into a conversation' online, without necessarily having any followers.
How do Hashtags work?
A Hashtag is a particular type of keyword that connects together articles of the same topic.
For example, if you posted to Facebook your favorite recipe for pumpkin pie, you might add the hashtags #pumpkinpie #thanksgivingrecipes #thanksgivingdessert #freepierecipes.
When your posting is published with these hashtags on Facebook -- or almost any other social media site -- when someone clicks a hashtag link on someone else's posting that contains one of the same hashtags as yours, your posting may appear in the list of postings. So, in the example above, if someone else had used the hashtag #thanksgivingrecipies in their posting, and someone clicks that, they may see a link to your posting in the list of related postings. If they click that link, they would be taken to your Facebook post. If your content is interesting enough, you may gather followers: people who are interested in see what else you post in the future.