What are the differences between a baby bike seat and a trailer for transporting children on a bicycle?

A baby bike seat is a small seat attached to the back of a bicycle where a child can sit while being transported. A trailer, on the other hand, is a separate compartment that attaches to the back of a bicycle and can hold one or more children. The main difference is that a baby bike seat is directly attached to the bike, while a trailer is a separate unit that is towed behind the bike.