"Toddler car seat" isn't a technical term. Car seats for toddlers can include convertible car seats and combination car seats (forward facing car seats that transition to booster). Since it's safest to keep your child rear-facing until as close to 4 as possible or even older, you'll want to make sure to buy a convertible car seat for a 2 year old. Most babies outgrow their infant car seats between 12 and 18 months and then transition to a convertible car seat. There are some convertible car seats that are outgrown by 3-4 years old, but most on the market today will accommodate kids until 6 years old (or even longer).