Can someone please explain this to me?

I don't get it at all.

Ditto.

Hi Keith.

its based on your kills assists and deaths. i believe but i know for certain assists are worth almost as much as kills.

Yep
Rewards players for kills and assists.
Somewhat for winning i think.

Your performance is ranked.
after 5 days your rank ( often around 1500) is averaged and you get ranked 1-5
5 being Onyx
1 being botard.

Thats how it was explained to me.
google it for more details