High percentage in similarity

1. When we compare two different faces it returns high similarity in face verification REST API what is the reason for that?
2. How many points does it uses when it makes face verification?
3. I saw that there are 5 main points and does that mean that it puts only 5 points to the face when it verifies user?
4. what type of algorithms does it use when it verifies user face?

I really need answers to all this questions, I would be very glad if someone could give me explanation to my questions

Thanks in advance