What is a memory ing file?

I have been confused about the meaning of the memory ing file. What I see on msdn today should be better understood:

Memory-mapped Files (mmfs) offer a unique memory management feature that allows
Applications to access files on disk in the same way they access dynamic
Memory-through pointers. With this capability you can map a view of all or part
Of a file on disk to a specific range of addresses within your process's address
Space. And once that is done, accessing the content of a memory-mapped file is
As simple as dereferencing a pointer in the designated range of addresses.

Original article address:

Http://msdn.microsoft.com/library/en-us/dngenlib/html/msdn_manamemo.asp? Frame = true