How does Back to My Mac work?
How does 'Back to My Mac' work?
MacBook Pro (13-inch Mid 2012), OS X Mountain Lion (10.8.3)
It's a use of VPN that enables you to access a computer remotely. You might use it when traveling to access your home computer from your travel computer. Of course you must leave the home computer turned on.
Mac OS X 10.7 Help- Use Back to My Mac
Setting up and using Back to My Mac with AirPort Express, Extreme or Time Capsule
Supported router devices for Back to My Mac
OS X- Using and troubleshooting Back to My Mac with your iCloud account