Facebook is the social network that defined what a social network was. It took real world social relationships into the digital world. Everything that people did offline, was now online on Facebook. You could have groups of friends, message them individually or in a group. Share posts and pictures, and most importantly get updates from all of the friends via News Feed. Facebook made it simple to stay updated with life events of everyone from your middle school friends to college friends.
Facebook has evolved over the years and has now changed fundamentally. If you login to Facebook today, you will not see status updates from friends, or pictures posted by friends. You will see news stories from Business Insider that were liked by your friends, or you might see other funny content like videos or memes that one your friends commented on. Facebook has turned from a social network to a media hub like Yahoo! was a decade ago. Except in this case, the content you see is what your friends like, so you might enjoy it as well (if you share a similar taste to your friends). Facebook also has Pages which allow brands like Pepsi or Unilever promote their products on the social media website, which show up as sponsored content in your feed. This is the new way to advertise products to the next generation. However, it has morphed a place where you communicated with friends and read about their life events, into a place where you go to read news you might be interested in, watch videos, and consume content that is created by an external website like Business Insider or one of the Facebook Pages that posts humorous content. Of course you might also see some updates posted by friends on rare occasions.