Crafting Recipe
Stick + coal/charcoal vertically = 4 torches. 1 coal -> 4 torches, highly efficient. Charcoal: smelt any log = functional equivalent to coal. No need to find coal on Day 1 — just smelt some logs.
Mob Prevention
Hostile mobs only spawn at light level 0. Torch provides level 14 on placed block, decaying 1 per block distance. Place every 7 blocks (diagonal 5, straight 4). Other max sources: sea lanterns/glowstone/jack-o'-lantern/redstone lamp/beacon = 15.
Light & Mob Spawning
Torches emit light level 14 and are the most cost-effective light source. Hostile mobs spawn only on blocks with light level 0 (some have different thresholds), so lining your tunnels with torches completely stops cave spawns — the foundation of safe mining.
Production & Alternatives
One coal plus one stick makes 4 torches; a stack of coal yields 256, so they are dirt cheap. For permanent lighting consider glowstone (15), redstone lamps (switchable), lanterns (15, hangable) or sea lanterns for better looks and control.