Resolve Permissions Errors Step #8
Above we have an image of a cow/milking farm. It is safe to assume that the network on this farm, is an "intranet". For the sake of this example we will assume there is not a need for an internet connection, as there is no need by the computers, software, or other machines required to maintain the farm, to have access to the internet.
The only people that need access are the employees working on the farm, all information or necessary software is already in place. Any updates to the system would be applied by a technician manually applying a patch (update to software).
Make sense? Good
Here we have an Extranet. You can tell the women are not working and they are all online laughing at the same photo because, well, because they are all at work, yet they are all laughing and smiling while sitting in front of their computer screens.
Which probably means they will all be accessing the work servers from home later that evening in order to actually complete the work they needed to get done that day, but were too busy laughing at "aweezz thaz so cuuutee!!" videos of furry kittens doing what furry kittens do, all day, instead of doing their jobs.
Anyway, all humour aside, the point is that a (most) businesses have an intranet with a connection to the internet, which makes that network an extranet....
Here we have a city, with hundreds of thousands of people, not all, but a majority of these people will have at least one device that connects to the internet, allowing them to connect to the rest of the people with devices in hundreds of Cities across the world (except for china, which again brings us back to that whole "internet an extranet, or extranet an intranet, is there really an internet if not ALL people can access it, well China? Is there?"...
On the internet your device is open to attacks/access from any other device.