Sometimes the phrase “induction compatible” is used by pan manufacturers to command a premium. In truth, any magnetic pan will work. The higher the ferrous (iron) content, the better. Many cheap steel or cast iron pans perform really well. A great simple and cheap compatibility test is a fridge magnet - the stronger the attraction to the bottom of the pan, the better it will work in general. Easy! Many stainless steel pans are magnetic, while some aluminum pans are made with a steel (iron) core, sandwiched in the base, so that they will work on induction. This type of pan generally works very well – the steel inducts, while the aluminum conducts the heat up the sides. It's true though that copper and all aluminum pans will not work. There is an approach to using induction on non-compatible pans that will allow for it, but it's prohibitively expensive and puts a lot of stress on the internal components. There's a cheaper alternative, too - to put a disk of compatible material between the cook top and the pan, but this is an inelegant solution and defeats most of the benefits of using induction!