If something goes up on the Internet, eventually someone is going to find it. But that doesn't mean you have to make it easy for them. There are certain things a Google+ page may want to say or share that isn't intended for all audiences. So Google has rolled out a few features that let people restrict who can see content based on age and country.
For clarification, these limitations apply to Google+ pages, such as the Android Police page, instead of individual profiles. The idea here is to help businesses and organizations better manager their PR. These options are present both for Google+ pages and individual profiles.
Page managers can access the options to tweak restrictions in a dedicated settings tab. They have the option to limit content to viewers who are 18+, 21+, or leave it open to everyone.
Clicking on the "custom" option reveals the ability to restrict content by country. There are various reasons to want to do this, such as if you're attempting to market a product that is only available in certain parts of the world.
For the full skinny on how all of this works, hit up Google's support page.