The usual classification is:
A network file system is
- a file system where clients can access data that is actually stored on other computers. Examples are AFS, SMB, NFS.
- the full name of the NFS network file system, initially developed by Sun Microsystems.
- a standardized protocol for compatible network file systems based on FS. Other vendors then Sun develop NFS servers, e.g. NetApp or EMC.
A distribution file system is another word for a network file system. It has the advantage that it is clearer that not necessarily NFS is meant.
A cluster file system is a file system where the data is distributed on multiple machines that appear to the clients as a single storage system (a cluster). Examples are PanFS, GPFS, Lustre, and to make things more complicate pNFS (Parallel NFS).