Reese Witherspoon asked son Deacon about the social media site TikTok in a funny Instagram post Sunday. “Deacon, this is very important. I’ve brought you here because I have questions for you,” Witherspoon said in the video, adding, "“What is TikTok?” People reports that Deacon described the site as "short-form video platform” where people shoot videos of themselves lip-syncing and dancing to popular songs. The Oscar-winner then started dancing, and got progressively sillier until her son finally laughed and said, "You look pretty cool." Witherspoon posted, "@deaconphillippe tries to teach me how to Tik Tok. I think I nailed it."