An inode used to be the on-disk structure that contained access permissions, ownership, size in bytes, and the disk block numbers of the disk blocks that contained a file's data. So, some metadata, and some data.
The file's name was just an entry in a specially-marked file, called a "directory". The name was associated with the "inode number".
Conceptually, all local filesystems still work this way, although directories are no longer just files with a special mark on them. There's still a separation between an on-disk chunk of metadata (including the data blocks of the file) and a directory entry. Directories for ReiserFS are a B-tree data structure on disk - I'm not sure if there's a B-tree for each directory, or if there's just a database like structure with all directories in it.
I say "local filesystems" because network filesystems like the famous NFS don't have to work that way at all. NetApp appliances can serve the same data with NFS and with CIFS, and the underlying on-disk structure is neither a Unix filesystem, or NTFS or a FAT filesystem.