Mountain Lion is the next version of the Mac OS. From the Mountain Lion press release:
“Gatekeeper is a revolutionary new security feature that gives you control over which apps can be downloaded and installed on your Mac. You can choose to install apps from any source, just as you do on a Mac today, or you can use the safer default setting to install apps from the Mac App Store, along with apps from developers that have a unique Developer ID from Apple. For maximum security, you can set Gatekeeper to only allow apps from the Mac App Store to be downloaded and installed.”
Get ready for the explosion.