Coal

Coal is two things in Minecraft, a block and an item.

Block

The coal block is found commonly in caves. Mining the coal block will deliver one piece of coal.

Item
Coal is used to make a Torch and powering a Furnace. Charcoal is also available, but we'll get to that later. Another use for coal is to power a Minecart.

Info Villager says

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Charcoal is made by putting wood in a furnace.