What are the differences between tiers an metagames?

Question

Beside the Pokemon in them, I mean what what defines the two and how they're different. I saw them on smogon.

Answer 1

The metagame is the fan-made term that describes Pokemon at a competitive standpoint.

When battling, putting Arceus against an Amoonguss is just unfair. That is why the metagame was split into tiers. Each tier has rules, to make things fair. Also, individual Pokemon were put into these tiers.

Answer 2

Metagame is what happens in the tier. It's almost the same thing.