The structural parts of the car between the floor panel and the roof structure are known as the A, B, C,(etc) pillar or post consecutively from the front of the car moving back towards the rear. This terminology is used by the motor industry for vehicle construction and the emergency services for vehicle destruction following a road traffic collision!
Some owners find the A pillar between the windscreen and the front side window glass very bulky and a hinderance to safe vision at junctions roundabouts, etc. Hope that explains Esson?!