Sam Gavin discusses three popular social media platforms - Facebook, Snapchat, and Instagram - in a school report. Facebook allows users to share content like opinions, links, photos, and videos with their profile and 1.44 billion monthly active users. Snapchat uniquely allows users to send self-taken photos and 10-second videos with messages and drawings to contacts that disappear after being viewed. Instagram focuses solely on sharing and viewing photos and videos among followers, and also functions as a photo editing software.