I have a 1991 honda accord dx my radio was stolen. im looking at some radio systems i came across 1 din or 2 din dvd players. im confused which is the right one to fit please help. thanks

DIN is the standard dimensions for car stereo head units. A single DIN unit measures 7" wide by 2" high. A double DIN is 7" wide and 4" high. Your vehicle can use either. You should get an installation kit to make the install look finished.
You can use a kit like the the Metra 95-7801
You can also get a mating harness that can plug into the factory connector like the Metra 70-1720
If your factory plug was cut when your radio was stolen you can get a replacement plug like the Metra 72-1720
Other manufacturers of kits are Best Kits, American International and Scosche.

A 1 DIN stereo is what came stock in your vehicle. A 2 din stereo is double the height of a 1 DIN stereo, but the same width.