They are headers, and if they are setup properly, they will extract the exhaust gasses from the motor better than stock headers. Given the limited room in the Gen3s, though, they are usually a convoluted design in an explorer, so their benefit is limited - they should still flow better than stock, but on a $ per hp gain, they are a fairly expensive, almost bling, mod.
You would be better off fitting a twin 2" system from the cats back - far cheaper, and from the cats back is more restrictive than from heads to cats. Just make sure you don't lose too much back pressure, or you will lose a lot of low down torque, so your truck may end up with more power, but it will get off the line like a tractor.