Security Groups Question

I'm very new to AWS, so apologise if I am asking what might be a ridiculous question.

I am trying to understand more about security groups. Based of what I found from reading various documentations... what I understand is there are two types of security groups. One is EC2-VPC which is an EC2 security group type and another is a VPC Security group. We can attach these security group types to other aws services such as ELB/NLB,S3 etc...am I wrong?

Also came across a RDS security group. Is that a different type of security group? How many types of Security Groups are there?