What is virtual memory used for?

What will be an ideal response?

Virtual memory is disk storage used to expand the capacity of the physical RAM installed in the computer. When the currently running programs and processes exceed the RAM, they treat disk space allocated for virtual memory just as if it were real memory. The disadvantage of this is that memory activities performed through virtual memory are not as fast as those performed in RAM (although disk access and data transfer speeds can be quite fast). Virtual memory works through a technique called paging, whereby blocks of information, called pages, are moved from RAM into virtual memory on disk.