What are the A, B, and C pillars on a vehicle and what are their functions?

Pillars are vertical structural supports connecting the roof to the body: A-pillar (windshield pillar) frames the windshield and protects in frontal crashes; B-pillar is between front and rear doors, providing side impact protection and door latching; C-pillar supports the rear of the roof. On SUVs/wagons, there may be a D-pillar at the rear. Pillars must balance structural strength with visibility requirements and contribute significantly to overall body stiffness and crash safety.