Hey, I don't even know what a bay leaf is
It can also be called laurel leaf
A cooking ingredient/spice(?) in many countries. It's used to give flavour, then removed after cooking, because the leaf itself isn't eaten. Not sure about specific countries, but it's used all over the world.
In my country it's super common in soups, and sometimes in braised meat. Never heard of a marinade with it though.