system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: How are chess players rated?
gpt
The Elo rating system. Players have a numerical rank that goes up when they win and down when they lose. When they win against someone with a lower rating than them, they don't get as many points as when they beat someone with a higher rank than them. If they lose against someone higher rated than them they don't lose as many points as if they lost to someone ranked below them.

This means you need to beat players of equivalent or greater skill (per the rating system) to increase your rank, but losing to an extremely highly rated player isn't very impactful unless you are also very highly rated. You can't easily rank up by beating players much worse than you, but losing to them is very detrimental.

Many other sports and eSports use a similar ranking system.