There are a lot of misconceptions about Circles in Google+ and a lot of people new to Google+ (otherwise known as G+ to many) just don’t ‘get it.’
Have no fear, I am here to try and explain it to you.
Firstly, Google chose Circles for one very important reason. We use social circles all the time in real life! It really is that simple. With G+ you can have a circle for your family, for your friends, for your business contacts, or for photographers you think take beautiful pictures. The list is endless and is entirely up to you. You really can make Google+ yours.
Once you have your circles, you can filter your main feed to posts from a specific circle. You can also post messages to a specific circle or circles. Anyone who is not in those circles will never see the message. So, friends and family will see your party pictures, colleagues will not.
The same applies to your profile. You can control the visibility of everything on your profile using circles. It is easy and very powerful.
When sharing things in G+, you will notice Public and Extended Circles are also options. Public is just that, everyone who has circled you, or who visits your profile will see your content. Extended Circles behave a little differently.
Your Extended Circles include everyone in your circles and everyone in their circles. If you post something to your Extended Circles, those you have circled will see your post in their feed, while the rest will see your post when they click on the posts tab of your profile.
Extended Circles also help G+ make suggestions on who you may know and like to circle yourself.
Finally, you can share circles! A brilliant way to connect with other people.