How does an AP course differ from a dual enrollment?

Dual enrollment is offered to students who are studying in high school, & have completed required courses. They can sign up for college classes taken at the college/online (at no cost to them) vs AP (advanced placement) which is a class offered at the high school, at the end of the course, the students can pay a fee to take a test, if they earn a high score, they will also have earned a college credit. If they do not pay the fee, they still have to take the test, however, if past they will not have earned college credit for it .