A child will most likely need to be in a car seat with a harness up to 5 years old. When they turn 5 then they will need to move to a booster seat until they reach the height and weight limits required by your state to be out of the booster seat.
You should keep your child rear facing in their child car seat until they outgrow the rear facing car seat and then you can move them to a forward facing car seat.
Usually after a year old the child is ready to move from rear facing and into a forward facing car seat until they're 5 years old.