DMA means Direct memory access, its used to get data's from
memory devices.....

U can see that an DMA controller is used to get data's from
floppy disk

DMA-Direct Memory Access.It means microprocessor can access 
datas present in the external memory (can be 
ROM,DRAM,EEPROM,etc) without CPU.

DMA basically used for speed up the data transfer 
using DMA it is possible to get fast data.....

DMA means Direct memory access ''for fast transfer of data 
between I/O devices and Memory devices and does not involve 
the microprocessor''