Need some help understanding this 🤨

Alright so I’m only 19 and still trying to figure out being an adult on my own. I just used credit karma to get my credit score and it’s 656 which isn’t bad but I would like it to be higher. How do I raise it? Also the only type of loan I’ve ever taken out was when I got my car and there has never been a late payment so why is my credit score only fair? I would have thought it would be good since my payments are always on time and I don’t borrow money and only use a debit card not credit