What it does
Earthbend isn't a real Magic: The Gathering keyword—it doesn't exist in any official rules, card set, or the Comprehensive Rules. It sounds like it's borrowed from Avatar: The Last Airbender, not from MTG.
You may be thinking of a similarly-named mechanic. For example, Landfall triggers abilities whenever a land enters the battlefield under your control, and is extremely common in green/landfall Commander decks. Alternatively, Bolster or Adapt put +1/+1 counters on creatures, which might be what you're picturing if "Earthbend" suggested growing or buffing.
If you saw "Earthbend" on a card, it's likely from a custom/unofficial set, a joke card, or a proxy. For accurate Commander rulings, double-check the card's actual Oracle text via Gatherer or Scryfall, since fan-made mechanics won't be legal in sanctioned play.
