You can change your name, photo, sites, gender, birthday and occupation. If you click the "+" button, you can also add work contact info, personal contact info, education, work history and places.
"You can change what other users of Google products see about you. For instance, when you connect with people on apps like Gmail or Hangouts, you can choose to share certain additional information with them, like your birthday and phone number," mentions Google's help center.
For now, the "view as public" feature doesn't work. "You'll soon be able to see what you look like to other people across Google services in this card. While we are working on it, view your public Google+ profile," suggests the site.
{ Thanks, Elchanan. }
