"TBT" stands for "Throwback Thursday" and is a social media trend where users submit content on a Thursday to commemorate a past event, thought or message. Usually, this activity involves posting a photo of something that has already happened. Common themes include images from childhood, important dates and major holidays.
While TBT participants usually post photos, they can also bring attention to an old social media quote or paragraph of text. These posts are generally tagged with "#TBT" or "TBT" to signify participation in the activity. Facebook, Instagram, Twitter and Tumblr are the most common social media platforms for Throwback Thursday to take place.