These recommendations are off the top of my head, so take with a pinch of salt [1] or better, verify them by looking up the terms (which you should do anyway to get any value out of the recommendations).
[1] Why I say "take with a pinch of salt" is because this is based on what I learned a while ago about Unix file systems (and some of the terms are also related to DOS and Windows), and some enhanced file systems have come out after that, so some of the terms I mention may be out of date (but likely not, or not many).
Look up these words and terms (not given in any logical order):
(Unix) inode, directory entry, file system, disk partition, physical partition, logical partition, fdisk, cfdisk, boot sector, boot record, master boot record, GRUB, LILO, boot loader, ext2, ext3, ext4, file system types, journaling file system, fsck, fsdb, superblocks, disk 'cylinders, heads, tracks and sectors', disk block size, buffer cache, logical volumes, disk spanning, disk striping, RAID, disk formatting, block device, character device, device file, device driver, ...
You will get many of those terms explained in the resources that others in this thread have mentioned. But this can be a fast way of getting an overview of many of these terms via Wikipedia articles or other pages about them, which may even motivate you to read the longer explanations.
If you are a programmer and know some C, you can also look up functions / system calls / man pages like stat, dirent, opendir, readdir, etc., and have some fun getting (and for some things, setting) the contents of directories programmatically, getting file metadata like file size, type, times (access, modification, etc., owner and group, permissions for owner, group, other, etc.)
Edited to add a few more terms.