The basics...Let's start with Facebook, the most popular.
Facebook is great to keep in touch with friends and family. Content goes through a “news feed” allowing for commenting on your post to Facebook. Your friends may appreciate a picture you have uploaded to your Facebook page and comment, 'oh what a cute dog,”. You may respond to a friend's post and press the "like" button. When you “like” something the friends in your network see what you like, as this content goes into their news feed. This keeps everyone connected.