A fireplace is required to create a heated room, which is required for smoking meat. Fireplaces in village saunas or inns will re-light by the villagers when they burn out. When wood stops burning in a fireplace, however, the embers continue to provide heat ("heated fireplace" meaning it can still be used to cook food) and acting essentially like a fire (for rituals and such). This keeps your cabin warm in the winter for longer using less wood.
It requires 6 firewood, 6 wooden stakes, or 5 firewood and 1 branch, or 38 branches to get started. You can also treat your frostbites near the fireplace providing heat. Tiles adjancent to the buring fireplace will not get burnt automatically.
All garbage (like rotten hide or sand mushroom) can be burned. Also good for burning inferior or poor boards.
To light a fireplace [p]ush fuel into it and light it the same way you light a fire.