The feature was first revealed in the spring, and it's aimed at substantially improving the simplicity of printing.
Cloud Print works by hosting printer drivers on your Google Account in the cloud. By keeping printer drivers decentralized with Cloud Print, users can avoid the hassle of repeatedly setting up a printer. Documents are then sent to Google, where they're interpreted and directed back to your printer to be converted to hard copy.
The feature bears some similarities to Apple's much touted AirPrint feature. A better parallel, though, is the ePrint functionality built into HP's latest printers. With ePrint, printers are assigned an e-mail address to which a user can send documents to be added to the print queue.
Since no Cloud Print-enabled printers yet exist, Google has built the functionality into the latest beta of the Chrome browser. For the time being, it only works with Windows, but support for other platforms is expected soon.