Car seats are designed to secure young children in the car with a seat belt. Infants, toddlers, and some older kids under a certain height must ride in a car seat or booster seat, as it's not safe for them to ride in a car with just a seat belt. Convertible car seats attach to a car seat to allow infants, toddlers, and some older children to ride safely in a vehicle.
The main difference between convertible car seats and other car seats for infants and older children is that they are designed to work as children grow. Adding padding, adjusting the seat height, or changing the orientation of the seat can help you make the car seat fit your child better.
Of course, it's important to follow manufacturer instructions and guidelines to use products safely.