Capacity, which represents the volume of information (in bits) of memory can store.
It is a combination of hardware and special operating system uses main memory and secondary to make it seem like your computer has much more main memory (RAM) than it actually possesses.
Access time corresponds to the time interval between the request for read / write and data availability.
Virtual memory has become an essential component of most current OS. And as at a given instant, in memory only have a few fragments of a given process, more processes ...