Hi Maria,
hashtags are any word that is preceded by a #. When you are in Instagram use the search feature to search hashtags to see which are popular. Hashtags work in Instagram, Twitter, Facebook, Pinterest, Flickr, Vine, Tumblr, Google+. I haven't found hashtags to be very helpful in Facebook or Pinterest but very helpful with Instagram and obviously Twitter.
Maria to use it in Instagram when you are typing your description any word you want to focus on use a # sign before it. A hashtag allows grouping of similarly tagged messages, and also allows an electronic search to return all messages that contain it. So I make crochet koozies. When I type my description in Instagram I will type a description like this: "Brand new #koozies on the #maroozi etsy store. Click link in my bio to start shopping." Then I will add a bunch of hashtags like #crochet #beer #craftbeer #koozie #coozie etc.
Some facts about hashtags:
- no spaces, multiple word phrases must contain no spaces i.e. #valentinesday instead of #valentines day (this would only make the word valentines searchable)
- no punctuation i.e. #valentinesday instead of #valentine'sday
- research your hashtags before using, some people have gotten into hot water by accidentally using a hashtag that may be related to something racy or just not something they want to be associated with.
Social Media Examiner -
http://www.socialmediaexaminer.com/hashtags/ and Marketing Land (more of a marketing industry professional site) are both great places for social media promotional ideas. I hope that helps. Happy to answer any further questions.