EZ Cap is a trademark for a brand of flip-top bottle. Some commercial beers are sold in this style bottle, notably Grolsch. Each bottle has a wire bail that holds a plastic or ceramic cap. You put a gasket on the cap, fill the bottle, then with your fingers push the bail to force the cap onto the bottle.
I've used them (I've got a bunch of Grolsch bottles) and they work fine. You don't need caps, and you can open them without a bottle opener (though to some, any tool is a bottle opener). They're also easy to re-seal if you don't pour everything out. And they look cool.
I personally find that my hands get tired before I finish bottling with them, though. A good capper with crown caps is easier.