Landfall is an ability word that triggers whenever a land enters the battlefield under your control. The effect varies by card—gaining life, making tokens, pumping creatures, dealing damage—but the trigger condition is always the same: a land entering, not a land being played.
The key nuance people miss is that landfall doesn't care how the land arrives. Playing a land for turn works, but so do fetch lands, ramp spells like Cultivate, blink effects, and recurring a land from the graveyard. Each individual land triggers it separately, so dropping multiple lands in a turn stacks the triggers. Importantly, lands leaving and returning count as new entries.
In Commander, landfall rewards greedy land-based strategies and shines with extra-land effects like Exploration, Azusa, or Scute Swarm. Fetch lands and Crucible of Worlds turn it into a repeatable engine across a long game.