The name "app store" is not quite correct. It's hard to imagine the point, in which from 30 to 70 percent of items were distributed free. Mobile "shops" were exactly that, except that "goods" they are intangible. Of course, to pay to download the programs Internet access is necessary anyway, so better choose the unlimited tariff.
From a technical point of view the mobile app store is a program that is part of the firmware of smartphone. Before using it, the client must pass a simple registration procedure in the app or in the phone browser or computer. After that login and password to log in to your account.
Running the store and entering account credentials, the user receives the ability to view the list of available applications. He can choose different categories and sometimes subcategories. You can also search for apps by key words and phrases.
After choosing the program, the user immediately receives information about its value. If she paid, he offered to pay her via SMS, credit card or virtual account, which can fill up through the payment machine. The list of available payment methods depends on the phone manufacturer. To pay for the purchase card is not recommended, as data can be intercepted by hackers. If the program is free, to start the process of downloading and installing by pressing just one button. Sometimes, though, after that enter the password.
Some mobile operating systems can be downloaded only in this way. Such, for example, iOS (for her store is called App Store) and Windows Phone 7 (Windows Phone Marketplace). Other platforms allow you to install apps from third-party sources, but the shop is still significantly easier and safer. Examples of such OS - Symbian 9 (Nokia Store, formerly Ovi Store) and Android (Google Play, formerly the Android Market).