How are rating scores determined for individual games? Previous discussion?

I've attempted to locate previous postings, but no luck. I am mystified by what factors are used to calculate how many points are given for a win or loss? A recent opponent lost 250 points. The game was not exceptional. My share of winnings? 6 points. Where's the justice?
If there is a concise answer, I'd like to hear it.

You probably skipped reading the giant red banner that said " Your question may already have an answer in the FAQ":

lichess.org/faq#ratings
lichess.org/faq#provisional

It's not really all that difficult to grasp...