All applications that follow the Metro design guides can be certified by Microsoft and available in the Windows Store.The Windows Store is Microsoft’s distribution point for apps for Windows 8. Apps in the Windows Store will be easy to discover and download. You can browse apps by category, ranking, top lists or see what is currently in the “Spotlight”.
Apps can be installed free of charge, as trials (for instance a trial for a certain number of days or a trial with selected features of the app available) or they can be paid apps. You can expect that the apps that are free of charge will contain advertising.
If you purchase an app in the Windows Store you have the right to install it on up to five PCs. When you sign in to the Windows Store you will be able to see the apps you have purchased so that you can easily install them on additional PCs.