that is pagefile.sys which is store in root drive of 
system, its contains virtual space of paging file.

The answer this question is:
VIRTUAL MEMORY- is the memory that is paged out to the hardware.

cache memory

ya its cache memory.

A CPU cache is a cache used by the central processing unit
of a computer to reduce the average time to access memory.
The cache is a smaller, faster memory which stores copies of
the data from the most frequently used main memory
locations. As long as most memory accesses are to cached
memory locations, the average latency of memory accesses
will be closer to the cache latency than to the latency of
main memory.

When the processor needs to read from or write to a location
in main memory, it first checks whether a copy of that data
is in the cache. If so, the processor immediately reads from
or writes to the cache, which is much faster than reading
from or writing to main memory.

read more in http://en.wikipedia.org/wiki/CPU_cache