Upload or UL U/L Download or DL D/L
This is the process of transferring an electronic file or files from one place to another usually whilst connected to the internet or intranet and using FTP protocol. Uploading and downloading is a frequent activity when creating, maintaining and running a website, so users are advised to install a reliable FTP client and learn how to configure connections to FTP accounts. Uploading file/s can also be achieved by using a web browser file manager. Some hosts will provide a file manager as part of the package. In many cases the file manager is an inferior method of transfering files, because there is often a limit to how many files can be uploaded at any onr time. Typically 5 or 10 files need to be selected from your distribution, then another batch selected, etc. untill all files have been uploaded. This method is very time intensive and prone to introducing distribution errors, (where files are sent to wrong directory destinations). File manager is a last resort method ... use FTP wherever possible as a whole root directory can be transferred at one go, maintaining the sub-folder/file distribution throughout the whole upload or download process.
More about this in "What is FTP".What is FTP?