It is commonly thought that to get "abs" you need to do lots of ab work (sit ups/crunches/planks etc). Although there is some truth meaning yes you need to build the ab muscles like any other muscle they need to be built, if you are carrying body fat around your stomach you won't see your abs no matter how much you train them.
So how do you get abs?
You need to lose body fat to see your abs. This means being in a calorie deficit (eating less calories than your body needs) and being consistent with this along with your training.
Everyone holds body fat in different areas and you cannot spot reduce. Your body decides where it will lose fat from first. You may look very lean on your arms or legs before you do on your stomach but over time and time spent weight training this can even out.