Also known as ‘filesystems’, the most common definition is the way how computer files and the data they contain is being stored logically so that it makes easier to find them on a storage device. Files on any computer regardless the operating system it uses, are being stored by using a hierarchical structure also known as a tree structure. Files can be manipulated easily i.e. they can be moved from one folder to another and organized as the user wants.  

There are conventions for naming files in which it is specified the maximum number of characters, what type of characters can be used as well as the number of characters used in the file extension or suffix.

Each data storage device has a file system software which organizes sectors (array of fixed-sized units or blocks) into files or/and folders. The file system software always keeps track of which sector belongs to a file.
Filesystems contain directories which associate file names with the files and the filename is connected to the index of a file allocation table which can be FAT, FAT32, NTFS or an inode in Unix type filesystems.

The file system usually stores the file creation date, the time it was last accessed or modified.

Most common types of file systems:

•    disk filesystems to store data on different kind of storage devices (hard drives): FAT, FAT32, NTFS, HFS
•    database filesystems when files are organized by their properties or characteristics:
a good ex: dbfs
•    network filesystems (it provides remote access to files on a server). Examples: NFS, SMB protocols
•    flash filesystems (specially designed to store data on flash memory devices)