Booster car seats are designed for children that are too big for an infant car seat and too small for the actual car seats. A booster seat can be thought of like an adaptor, they fit into the automobile seat and the child fits into the booster. And unlike an infant car seat, the child uses the lap and shoulder belt of the car rather than a 5-point harness.
As a general rule, booster car seats are actually less expensive than infant car seats. Of course, this depends on the type of infant seat that is being compared to the booster. A quality booster seat can cost as little as 50-100 dollars, but can also go as high as 200-300 dollars.
Booster car seats come in a number of different designs. The most basic boosters are simple “seat” with no back. However, for those that want a more unique look, boosters are also made to resemble racing seats.