In Linux virtual file system, every file / directory is mapped to an object named “inode”. It is a data structure that stored the necessary metadata about the file, instead of content of the file itself.
Below is a great video tutorial from Youtube made by “theurbanpenguin” that was super helpful for me to learn what inode is.

A few handy commands:

ln file1 file2  # this will create a hard link file2 linked to the content of file1
stat f1    # this command will get the inode information