is a DDR and a DVR the same?
To a certain extent. DDR's and DVR's are the same thing. The only real difference is that DDR's are used by people in the media, and DVR's are used by people at home.
DDR's also usualy have *way* more recording space and abilities where as a PVR can only record smaller amounts and simply plays it back.
Most DVR's can record 160GB meaning about 150 hours of recordings where as most DDR's have 8 SATA Raid drives at 500GB a peice.. Meaning exactly 3.90625 terabytes of recording space which is about 166.666667 days of recording.