The simple answer is data saved on your computer.
e.g. if you visit a website where you shop for any products, these details usually known as the basket, are saved on your computer in a file called a cookie. The reason for this is in case either the website, your computer or your connection to the website fails the name or products are remembered, so that when you return to that website the shopping can continue at the point the failure occurred. It is in the interest of the shop that the goods already in your basket are not lost as you would probably not bother searching the site again for all your products if you had a failure.