Hashtags are added to tweets with a number sign in front of their name.
Hashtags, for example, make it easy for you to find people who are talking about the same topic.
Hashtags also show what subjects are trending on Twitter, and often revolve around events, holidays, special occasions, sports or entertainment events, celebrities, and major news items.
Now that you're more familiar with Twitter you can explore other options, like learning about hashtags and incorporating third-party applications to make the service even more dynamic.
Hashtags are like keywords, indicated on Twitter with the # sign, which make them clickable for others.