Google + is a service of Google. It was started by Google to stand up for competition in front of FB. Now a days it's also getting popularity. You can share information their. You do not need to make a individual account for it. Its connected to Google account.
Google is a very popular site for most of the users , because it has great use of visitors and have lot of information with millions of sites. you have to use regularly.
Google+ is a social media platform to get connected over world wide. It is just like other social sites (facebook) to share your images, videos and updates and via Google+ you can promote an online business to share online products and services.
I think before Google plus, Google has many services that should be included to social network. like chats, photo sharing, groups. Google plus interconnected those services and really amazed to see that single gmail Id can do that much of things.