First I will Tell you that Facebook have daily active users is 1.50 Billion. so thats why facebook is biggest Social Network Website.
Facebook Is Very easy and very simple and cool design. facebook app is best beacause I think that we can see the hole things like you can chat with your friends and with your family and see the photos where somebody is gone.
The Facebook have most features like your can share your photos and videos etc., facebook have a emoji that is very cool thing that other person feel that what is your reaction, you can tag your friends, facebook notify you yours friends birthday, your friends status like that your friends get married, where your friend traveling etc.
The use full thing on facebook that your can create your own page if you have any great knowledge you can share on your page and hole followers can see and you can growth your status that’s the power of facebook.