There are 3 weight groups of car seats. Baby car seats - are with "0" symbol (to 10 kg) and 0+ (to 13 kg). That seats provide safety to theese babies - they can not sit in car in front-facing position.
Babies always must be in laying or half laying positions in car. And they can be in car seat maximum 2 hours in succession. This small body can not travel long. We have to provide comfort and safety for it.
Car seats can be installed by safety harness or special ISOFix system. This system works thanks to special hinges that are in car and special stabilisation leg. Some producers offer ISOFix bases in wich you can pin on higher groups car seats.
When we are selecting the car seat we must see its marks in independent crash-tests. We must chceck whether the car seat can be pined onto our stroller. Thanks to this You have comfort during a shopping. You don't need to take big carrycot. It is good when car seat has extensive peak against sun. You have possibility of set a comfort lying position during car drive or pushing a stroller.