It's basically a rice roll. It's one of my favourite Korean foods. You can buy one for W1000 (about AUD$1.30), so it's pretty cheap, too (one is plenty for a meal).
Well, here are some pics.
It has rice (obviously), carrot, egg, ham, and two other veggies I have yet to satisfactorily identify; all in all: delicious.
Captain Kimbap. "Hana kimbap, chuseyo."