Microsoft, like many other companies, has an affiliate program where you can earn additional revenue on your website (or similar) by selling the company's products such as Surface, Xbox, PCs, Phones and Office 365. If a consumer uses your link to buy a product, you will receive a portion of the sale.
The company has now expanded the program and opened the doors for content owners to obtain commission for anything sold through the Windows Store. Microsoft is offering up to 10% commission with an attribution window of 14 days for in-app purchases.
If you are interested in this program, you do need to apply (source link below) and must be approved to become an authorized affiliate. Seeing as Microsoft expects Windows 10 to be on a billion machines within three years, a lot of apps will soon be purchased by consumers which means this channel could become a lucrative options for driving revenue.
The reason Microsoft offers this type of program is simple: it allows website owners to act as sales agents for the company to generate revenue for their business, and for Microsoft, they gain new customers with minimal marketing effort through the program.