Gatekeeper is a 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.
Apple Developer ID
As part of the Mac Developer Program, Apple gives developers a unique Developer ID for signing their apps. A developerís digital signature allows Gatekeeper to verify that their app is not known malware and that it hasnít been tampered with.
If an app doesnít have a Developer ID associated with it, Gatekeeper can let you know before you install it.