File System
File systems means how the storage is used organized and used by the operating system.
The storage systems refer to hardware which has physical space and firmware on top of it which physically reads and writes to specific addresses.
While file systems refer to the software which then utilizes the storage system to have an hierarchical directory structure on top of a plain disk, control its permissions, etc. The file system software then decides how it would like to use this plain storage.
Formatting a disk
When we format a disk, it basically means the storage is prepared to be used by a specific software such as ext4, NTFS, FAT, etc.
It means the clearing the existing data and creating super block of that storage, root inode information, etc.
For the underlying storage, super block and other information are just stored in a regular place. It has no special meaning for the storage hardware itself.
Map file systems to mount points
fstab file has the mapping of all file systems to different directory in the full file structure hierarchy.
This file shows which storage system is mounted at which directory.
When system boots, all hardware is detected and using the data at /etc/fstab they're mounted (linked) to different directories and depending on the file system type in this file, the VFS then speaks to the underlying storage system to get files and directories information.
Device Drivers
These are the common methods called by the ext4 methods irrespective of the underlying storage manufacturer.
Storage Firmware
These are the storage manufacturer methods invoked by device drivers.
File system block size
It's the minium size used by the file system to manage files. This means, if the block size is 4KB, even a file with just one letter with block 4KB space on storage. Mostly the size of the block is kept same as the physical sector size for better performance.
sectors sizes are something managed by the firmware.
Partition
A physical disk can be logically split into multiple logical disks and each logical disk can be formatted into a completely different file system.
This partitioning of the physical storage is completely transparent to the storage and it's firmware.