When you download Amazon Cloud Drive, you'll automatically start a free 3-month trial. Then, as with many other storage services, you'll need to pay to keep using it.
Amazon Cloud Drive automatically organizes all your files into documents, images, videos, and Kindle files. And because it's Amazon, you can also quickly access all the documents on your Kindle reader.
Amazon Cloud Drive is a powerful cloud-storage service that offers a simple and elegant interface (though it's perhaps too similar to Dropbox).