Private places on your body are the places which God covered on Adam and Eve in the Garden of Eden. They are places that God does not want others to touch. Some people say that private places are the places covered by a bathing suit. It is not that simple. There are places on your body not covered by bathing suits that other people should not touch.
Private places are different between boys and girls.
Let me use pictures to help you understand where the private places are. For a girl, private places should be the areas under the yellow shaded boxes in the picture to the left. Above the elbows to the shoulders in front and the sides. Below the waist above the knees in front and back and all sides. For a boy, private places should be the areas under the yellow shaded box in the picture to the right.