OS X Mountain Lion: About screen sharing
With Mac OS X v10.5 and later, you can connect to another computer on your network and display that computer’s screen on your computer. While you share the computer’s screen, you can control what happens on that computer, such as opening documents or applications, opening, moving, or closing windows, and even shutting down the computer.
You can also share your computer’s screen with another computer on your network.
Screen sharing can be useful if you need to access a computer at home while you’re away from home. It can also be useful if you’re trying to solve a problem on someone else’s computer or you want to collaborate with someone on a project, such as building a website or creating a presentation.
OS X screen sharing is compatible with Virtual Network Computing (VNC), an industry standard for remote-controlling computers on a network using TCP/IP. It is also compatible with Apple Remote Desktop v2.1 or later.
If you have an iCloud account, you can use Back to My Mac to share the screen of any computer that has your account name and password entered in the iCloud pane of System Preferences, even if that computer is on a remote network.