What are "the arenas"?

Blind rating battlegrounds, one is https://lmarena.ai/ (first google result)

I don't quite get what this is? I asked the AI on the site "What is imarena.ai?" and it just gave some hallucinated answer that made no sense.

People vote on the performance of AI, generating ranking boards.

	▲	kstenerud 7 days ago \| parent [-]
		Ah, that was the missing piece of information! Thanks!