@ProudKulak I LOOKED AT GOOGLE IMAGES AND LOOKS LIKE THESE TWO ONCE PRACTICAL STYLES BECAME DECORATIVE AND KIND OF MERGED INTO EACH OTHER

ORIGINALLY TRAY CEILINGS WERE JUST A WAY TO GET MORE CEILING HEIGHT
INSTEAD OF SETTING THE CEILING ON TOP OF THE HOUSE WALLS AND HAVING A TRIANGLE ATTIC ABOVE IT, IN THE PITCHED ROOF, YOU CUT BACK AND SET THE CEILING ON THE PITCHED SIDES OF THE ROOF
YOU'RE STEALING ATTIC SPACE INTO YOUR MAIN ROOM SPACE

MODERN ONES ITS ALL MOULDED OVER AND PRETTIED UP WITH NO PRACTICAL CONSIDERATION