inode

In a file system, file names, e.g. my-doc.txt, are associated with inode numbers. And in a file system implementation, inode numbers are associated with blocks on the disk that contain the data for the corresponding file. This information lives on the disk in the inode table.

Note that there is one file system per partition, and each one has it's own inode table.

So the procedure that you (or an application) would follow for looking up a file at a path name is:

1. find inode number for directory
2. go to the directory's inode in the file system implementation on the mounted partition. This will contain the directory structure
3. find the filename you want in the directory structure and go to the associated inode. (If the filename is another directory, we're going back to step 1)
4. Repeat until you reach the file data you're looking for