Sun's NFS protocol provides transparent remote access to shared file systems across networks. The NFS protocol is designed to be machine, operating system, network architecture, and transport protocol independent. This independence is achieved through the use of Remote Procedure Call (RPC) primitives built on top of an eXternal Data Representation (XDR).

The supporting MOUNT protocol performs the operating system-specific functions that allow clients to attach remote folder trees to a point within the local file system. The mount process also allows the server to grant remote access privileges to a restricted set of clients via export control.

The Lock Manager provides support for file locking when used in the NFS environment. The Network Lock Manager (NLM) protocol isolates the inherently stateful aspects of file locking into a separate protocol.

Source: http://www.networksorcery.com/enp/protocol/nfs.htm

See the manual: nfs.