A collision refers to any instance where two or more objects, such as vehicles, come into contact with each other. It is a general term that encompasses various types of accidents involving vehicles, such as rear-end collisions, side-impact collisions, and others. On the other hand, a head-on collision is a specific type of collision where two vehicles traveling in opposite directions collide with their front ends facing each other. In a head-on collision, the impact occurs between the front sections of the vehicles, often resulting in severe damage and a higher risk of injuries or fatalities.