The Federal Trade Commission is seeking information from Facebook, Twitter and other social media and video-streaming companies including WhatsApp, Amazon, TikTok, Reddit, and YouTube about how they use the personal information that they collect on their users, the United States’s agency said on Monday. The Commission is seeking to learn how the companies collect data on users, how they decide which advertisements to show, and how algorithms are used, among other information, the agency said in a statement. It is also seeking information about how the companies’ practices affect children and teenagers.