Both upload and download refer to the process of transferring a file. When you transfer a file, you create a copy in the location you choose.
Upload means to transfer a file or files from your own computer to another computer. For instance, you might transfer a file from your home PC to the Yahoo! computer that stores your Web Hosting files.
Download means to transfer a file from another computer to your own. You might download a file from your Web Hosting account to your home PC.

FTP is the quickest way to upload and download files. Learn how.