File system
A File system (or filesystem) is a way of storing all data on a data storage device. The data is usually organized in computer files in directories. Below the file system there is usually a physical device where the files are stored.  This might be a hard disk, USB flash drive, compact disc, or DVD. The file system might also talk to a remote server over a network where the file is stored. The file system might also only use RAM to store the files.