Abs are made in the kitchen. Don't be misled into believing that doing ab exercises is going to magically give you great-looking abs. You cannot spot-reduce, meaning, you CANNOT simply focus your workout on a specific area on your body in order to melt the fat from "that spot". It doesn't work like that.
And of course, without melting the layers off your belly, you'll never see those hard-earned abs (or even a flatter mid-section).
Doing ab exercises alone will NOT be enough to burn off fat. Cardio and strength training can certainly help melt those layers, but that won't work as effectively if you don't clean up your foods!!
Let me give you an example: The photo on the left is what my abs would look like when I eat normal, enjoying some of my fun foods (in moderation, of course), and keeping up with 2-3 strong workouts a week. The 2nd photo (to the top right), I didn't do anything different. I kept up with my usual workouts. The only difference I made was that I started eating super clean for a week.
Then, I continued this clean-eating regimen for another 7 days, adding a little more core exercises, and bam! Six pack abs showed through, as you can see in the last 2 photos (ok, I was flexing, hee hee). Anyway, you get the picture!
"Clean eating" means balanced meals including all macronutrients (carbs, protein, fats) and keeping foods as close to their natural state as possible (nothing fried, greasy, creamy or cheesy). And of course, this also means consuming the right portion sizes of food to cater to your body size and activity level.