Infant Car Seats actually come in two parts. There is a base, which is latched and buckled into the car, and the actual “seat” which is detachable and is locked into the base piece. The car seat is always rear facing to better support the neck of the child in the event of a front-end collision.
(This is a Chicco KeyFit 30 – notice the base piece that locks into your car, and the handled and detachable “seat”)
Infant car seats are typically meant to support the child up until its first birthday, but depending on the size of your child can be used for a little longer. Their weight limit is usually in the 22-36 pound range.
Infant car seats can range dramatically in price, features, interchangeability (a Graco car seat will usually work in the base of another Graco car seat, but not the base of a different brand), and safety, although generally speaking any new* car seat sold in the US has to meet basic federal guidelines for safety.
When purchasing an Infant Car Seat, it may help to buy multiple car seat bases. In the case of multiple caregivers using multiple vehicles, uninstalling and reinstalling a single base can become a hassle. Bases are relatively affordable and easily allow Mom, Dad, Grandparents, a Nanny, et al to simply lift a car seat out of one car and snap it into their own base. Often, these car seats can also snap into a like-branded stroller, making them exceptionally convenient.
(Here is the Evenflow Journey Stroller – notice how the car seat fits snugly inside)
Convenience is the main purpose of the infant car seats. Generally, experts say that a properly padded and fitted rear-facing convertible car seat is also infant friendly, and if you’re looking to save money, you’re going to have to buy a convertible car seat anyway. That said, convertible car seats are a bit larger, aren’t really meant to be moved from car to car, and have a much more limited stroller-compatible selection. Still, once your child has outgrown his or her infant car seat, you’ll be moving on to an Infant to Toddler Convertible Car Seat.