It varies by gender, age and ethnicity, but overall if your body fat is over 30 you're considered overweight and possibly obese. Under 20 is generally the body fat of pro athletes like marathon runners or weight lifters. Staying in the mid-20s range is a good goal and considered the norm.
Mhm.. well, as I have done researches for me, I think that normal body fat percentage is about 15%. If you have more then 15% it can be burned easy with exercices.