Hashtag is a word or phrase preceded by a hash sign (#), used on social media websites and applications, especially Twitter, to identify digital content on a specific topic.
It is a popular way of categorizing social media updates. The combination of the pound symbol # with a keyword is hyperlinked in social media, allowing to search for and find relevant content related to the keyword.
If we think about how hashtags have been used on Twitter, it is very similar to how they are used on other platforms. Instagram, LinkedIn, even Facebook (to a MUCH lesser extent). This way hashtags make content discoverable and allow people to connect with other social media users interested in a given topic.
Now you know the reason why I use 15-20 hashtag in my post. 😅