What is a file system ? How is it useful ?

A file system is a part of operating system that is responsible for organizing and retrieving files from a storage device.

A file system is useful as it performs the following functions :

1. Creating a structure on storage device to store files.
2. Specifying file naming conventions, such as the maximum number of characters in a file name, which characters can be used and, in some systems, how long the file name suffix can be.
3. Specifying format for specifying the path to a file through the structure of directories.
4. Providing a way to access/retrieve stored files.

So, the user application when trying to access a file, interact with the File system component of operating system, which then interact with actual hardware i.e., the storage device and retrieves the asked file.