Toddlers use both hands and feet equally. Becoming aware that you have a left and right develops during kindergarten.
To make automatic movements you develop a preference side with your hands, feet, eyes, ears and brain. Both sides will also learn to work together.
You not only have left and right side but also a bottom / top and front / back. Babies start with this skill by crawling. Laterality is the pioneer in developing sense of direction.
There is an imaginary middle line between the left / right, front / back and bottom/ top. It is a challenge for toddlers to simultaneously moves the left hand and right leg. This should be practiced and learned. Also, to move the your left hand to the right side of the body is still difficult for toddlers.
For complex skills, such as maths, reading and writing, this development is very important. This development is completed around 8 years old. It is an enormous challenge to start reading, writing and arithmetic as the body is not yet fully developed.