Before this tutorial, our total discussion or tutorial has assumed that the virtual memory is transparent to the processes and computer programmers, that is, all they see in a big virtual address space on a computer system with small physical memory.
That's true with many computer systems, but in several advanced computer systems, computer programmers have some control over memory map, and can use it in non-traditional ways to enhance the program behaviour.
A solid reason for giving the computer programmers, a control over their memory map is just to allow multiple processes to share the same memory.
It is possible for one process to give another process, the name of a memory region so that the process can also map it in, only if the computer programmers can name the regions of their memory.
High bandwidth sharing becomes possible with multiple processes sharing the same pages, that is, one process writes into shared memory and another one reads from it.