Read this: The Xbox Live Marketplace is a virtual market designed for the console that allows Xbox Live users to download purchased or promotional content. The service offers movie and game trailers, game demos, Xbox Live Arcade games and Xbox 360 Dashboard themes as well as add-on game content (items, costumes, levels etc.). These features are available to both Free and Gold members on Xbox Live. A hard drive or memory unit is required to store products purchased from Xbox Live Marketplace. In order to download priced content, users are required to purchase Microsoft Points for use as scrip; though some products (such as trailers and demos) are free to download. Microsoft Points can be obtained through prepaid cards in 1,600 and 4,000-point denominations. Microsoft Points can also be purchased through Xbox Live with a credit card in 500, 1,000, 2,000 and 5,000-point denominations. Users are able to view items available to download on the service through a PC via the Xbox Live Marketplace website. An estimated seventy percent of Xbox Live users have downloaded items from the Marketplace.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): What XBox Live service allows users to buy games and downloadable content?
Xbox Live Marketplace