Dig. Build. Craft. Survive the dark beneath.
Every world is generated from a seed: snowy peaks to the west, deep forest where you wake, a burning desert to the east, and something purple and wrong at the edge of the map.
Mine ores, smelt bars in a Furnace, hammer out gear at an Anvil, and dig deeper. Break Heart Crystals for more life. Loot chests in forgotten cabins. At night, the eyes come out — collect six lenses and craft a Suspicious Eye to summon what watches from below.
Walls do not stop monsters, but light and a roof help you see them coming. Place torches. Keep healing potions in your hotbar. If you die you respawn at your spawn point — your items stay with you.