What is a file system?
A file system is a OS program - that facilitates file organization and access. The storage devices have no idea of what a file is.
The storage device is all about storing the bits. I think the file system is what that gives the context to the files. Or the files system has the criteria of identifying what’s a file or what qualifies to be a file in a storage device.
File systems are part of OS that manages the file organization and access. The file system can be understood as layers of abstraction over the data. The logical filesystem has to provide api for applications for operations like open, close, read, write. The physical filesystem has to deal with the representation of files in the storage devices, however actual implementation might not differentiate the process operations
File system hierarchy in linux
/ — root of everything /bin — essential system commands /sbin — essential system admin commands /usr/bin — most user commands /usr/lib — libraries /lib — core libraries /etc — config files /var — logs, caches, spool /home — user homes /root — root user home /tmp — temp files /boot — kernel + bootloader stuff /dev — device files /proc — virtual info about processes /sys — virtual info about hardware /mnt, /media — mount points