Laws of motion say that any moving body has a momentum (inertia) which depends on the weight of the object and its velocity. Inertia is the resistance of bodies to oppose changes in direction or speed, whether those bodies are in motion (dynamic) or at rest (static).
For everyone meaning, in case of an accident, there are several elements that suddenly change inertia: the car itself, passengers and objects from the car. If the car suddenly stops due to an impact, the objects inside, and passengers will tend to move on.
In the case of the automobile, inertia is related to changes of direction, in general at transition from a regime running in a straight line to one of a turn and vice versa.
The importance of inertia and mass/weight distribution is related to how fast it will make the transition from one regime of movement to another (from movement in a straight line to movement in turn and vice versa). Although these changes given by inertia and vehicle mass distribution may not be very high in case of a car, the changes would be greater in case of excessive weight positioned in the back of the trunk (as far away form the rear axle) or roof rack, this scenario drastically changing the car handling.
Since inertia makes any moving body to continue to move in a given direction, another force will must be applied in order to make that body to change its direction (to steer, in the case of vehicle). This force is called Centripetal Force and is the result of the tires trying to change the direction of movement. Centripetal force must exceed the value of the centrifugal force so that the car can perform a turn.