Amazon began in 1995 selling books from Jeff Bezos' garage. It now operates websites in seven countries using a network of 21 warehouses totaling over 9 million square feet. Amazon relies heavily on Linux technology to run its databases and securely process transactions. In addition to individual customer sales, Amazon allows large retailers to sell through its platform while fulfilling orders through the retailers' own websites. Amazon tracks customer data across purchases and recommendations to target relevant products to users. Some have expressed privacy concerns over the data sharing between Amazon and its partners. Overall, Amazon has grown significantly from its start as an online bookseller to become a large global retailer offering a wide variety of products.