Apple has not given the exact time of the launch. It is expected that Mac App store will be available by 12.00 PM (US local time) Jan 6. The Mac App Store will be similar to Apple's popular application store, Apple Store, where users can easily identify and purchase applications for their computers.
Apple is planning to launch the Mac App store in 90 countries, Later it will be extended to other parts of the world. In Mac App Store users can browse Mac apps by category, such as games, productivity, music and more.
Mac App store also allows quick search for something specific, read developer descriptions and user reviews, flip through screenshots and finally click to but the specific application.