The ETT (red) has been placed with its tip (asterisk) in the right main bronchus.
The arrow shows open airways which are comparatively black (arrowhead), seen against collapsed lung, which is comparatively white. This is an example of 'air bronchogram,' which in this case is due to lung collapse, caused by under-ventilation of the left lung.
The anaesthetist repositioned the tube above the carina and a repeat X-ray showed re-expansion of the left lung.