In its simplest form: body fat is the amount of fat in your body, compared to everything else. Everything else includes your organs, muscles, bones, tendons, water, and so on.
Both men and women carry different amounts of body fat percentage due to…you know…being different.
A super ripped male body builder who is minimizing body fat percentage could have a percentage down as low as 3-4%, while a super ripped female body builder who is minimizing body fat percentage would only get as low as 8-9%. A male athlete could be in fantastic shape and have 10% body fat, while a women at comparable level of athleticism and appearance might be at 18-20% body fat. To take the comparison to the other end of the spectrum, an overweight male at 30% will look vastly different than an overweight woman at 30%