Virtual Memory

• Programs locate data using a virtual memory address, which can refer to a location in the system's random access memory (RAM), on the hard drive, on a portable flash drive or other storage mediums. The operating system translates virtual addresses into specific physical addresses. Most programs are unaware of where their data is physically stored.
  
  

Paging

• Paging is the process of moving small pieces of data, called "Pages," from one storage device to another. Generally, as one page is moved, another is swapped into its place. In most cases, the exchange is between a system's RAM and the hard drive. In some implementations, the space used on the hard drive is called a "Pagefile."
  
  

Function

• RAM is the fastest storage medium in a computer, but it comes in relatively small capacities. If a collection of running programs require more memory than a computer has in RAM, then some of the data must be moved or some programs will cease to work. By using a larger, but slower, storage device like the hard drive, the system's memory space can be virtually extended.