The word ‘omurice’ is a contraction of the words ‘omelet’ and ‘rice’ — guess what the ingredients are??
Well, besides the obvious eggs and rice, you can put all kinds of things in (or on, or around) omurice! Usually there is a mix of meat and vegetables in the rice, along with a little bit of ketchup (to give the rice a nice pink color). This is molded into a football shape, then a cooked egg is draped over the top, and the whole thing gets drizzled with ketchup. That, essentially, is omurice.
However, you can do all kinds of things with it! I made it for the first time tonight, and I added broccoli, carrots, and onions to the rice and left out the meat. It was unbelievably good. When I ate it at a restaurant in Nagano station, I had it with a crab croquette on top and a meat sauce around it; you can also get it with stew, curry, covered in mayo, or a number of different ways.
Updated 12/6/17 with another picture of omurice!
Updated 1/11/18 with picture number four!