A mapping that associates the pathnames used in URL to the file system maintained by the host machine's operating system.

a file which contains multiple files, potentially in a hierachy

a kernel software layer that handles all the system calls related to a standard Linux file system

A remote file system that has been mounted so that it is accessible to the local user.

A virtual file system (VFS) or virtual filesystem switch is an abstraction layer on top of a more concrete file system. The purpose of a VFS is to allow for client applications to access different types of concrete file systems in a uniform way. A VFS can for example be used to access local and network storage devices transparently without the client application noticing the difference.