The secret behind these types of erasers is a material commonly called melamine foam.
Melamine foam erasers are formed differently from other cleaning products and only need water to effectively clean most stains -- no chemical cleaners or soaps required.
Melamine foam erasers work well; but on surfaces that are painted, polished or easily scratched, they might work a little too well. It's recommended to test the eraser on a small, preferably unnoticeable, portion of whatever you're looking to clean before you dive on in.
With just a little water, The Magic Eraser can dig in and destroy stains that other products can't touch.