How am I meant to use these trays that came with my oven? A Turkish oven we recently purchased has no thermostat, but it did come with two metal trays. They are like (American) broiler trays but without a cooking rack.

I could believe that they are just broiler trays, but (1) there are two of them; (2) I believe I have seen people adjusting the position of these trays in similar ovens when making bread.

What are they for, and how can I learn to use them appropriately?

Picture of an oven with and without the aforementioned trays
Unlike American ovens, some European ovens come with built-in baking trays.  These are designed to slide in and out using the oven rails, and take the place of sheet pans that you would put on top of a rack in an American oven.

They're actually quite convenient, except that there's only two of them.

For example, if you watch this Spanish cookie video, you'll see that Albert is using one of those pans to bake cookies.