Once you have mastered a regular cartwheel, and then a one-handed cartwheel, you are ready to begin learning how to do an aerial. An aerial is similar to a cartwheel, but no hands touch the mat. These two girls have mastered the art of doing an aerial and give very clear instructions. However, I advise that you have a professional instructor teach you.
I think these two girls will make excellent gymnastics instructors some day. They articulate and demonstrate this gymnastics lesson on the steps to doing an aerial very clearly!