Social media refers to online platforms that allow users to create and share content with other users or networks. Popular social media sites include Facebook, which launched in 2004 and allows users to connect with friends and share photos and updates, Twitter, which launched in 2006 and allows users to share short messages called tweets, and LinkedIn, which launched in 2003 and focuses on professional networking. These sites facilitate interaction and conversation through features like sharing, messaging, and community building.