Infant car seat and regular car seat

Dina👸🏻🇧🇦 • FTM. Animal lover. Strong supporter of vaccines, BLM, LGBT, & getting petty when someone tries me. 🤷🏽‍♀️
So I keep seeing posts about infant car seats and other car seats. I'm a ftm and thought all car seats could work for babies of any age up until they reach a certain weight. I was going to buy a car seat and stroller but now I'm not sure how to. What's the difference? Is my newborn allowed to sit into any car seat? How do I know which to buy? Helppp please 😣