Booster Seat What Is The Difference Between A Car Seat And A Booster Seat?

What is the difference between a car seat and a booster seat? - booster seat

My daughter is 4 1 / 2 and she is 52 pounds. The car seat we have up to 100 pounds. Does this mean that we can stay there or not, it is necessary to move into a booster seat soon? I have no idea. Thanks