First Pap smear.... nervous

I am going to get my first Pap smear next week. I’m really nervous. What does it test for? If it comes back abnormal does that mean std? Will they know exactly why it’s abnormal? I am very nervous and I hope it doesn’t hurt. I’m embarrassed to talk about it because my mom passed away when I was 11 and we didn’t get to talk about things like this and I do not feel comfortable talking to my dad so I come here. I don’t really have any close female family members that I feel comfortable asking these questions to. It feels like I have a mother figure when it comes to asking questions on this app