TBT stands for Throwback Thursday. It is one of the widely used hashtags on social media. It refers to a weekly social media posting trend and hashtag game used by people to share or look back on their favourite moments, so it got a "throwback" theme, which can be used for almost anything that happened in the past.
Anyone can participate in the TBT trend by sharing or posting content on social networking sites like Twitter, Tumblr, Facebook, or Instagram to talk about a past event. The post can be a photo from years ago or just a few days ago. It offers a way for people to post more about themselves.
To use TBT, you are not required to have thousands of followers or to be a social media superstar. You just need to have something interesting to post about the past and tag it with #Throwback Thursday, #Throwback or #TBT, etc.