Map projections are nothing to understand after reading a few sentences.
But here are a few links I find helpful.
But to make it short. UTM coordinates are not given in lat/lon but in meter. It’s the distance to a reference point. But they can be translated into lat/lon. That’s what we do in SNAP. We show lat/lon as default. But you can also have a look at the map coordinates. Open the Pixel Info View to do so.