Building a fire in a survival game is an important early-game milestone: it lets you stay warm and toasty even when the temperature drops, and you can start cooking basic meals instead of just stuffing berries into your face. At night you can see a few feet around your fire without having to hold a torch, and even more importantly, you can spot your campsite from a distance while blundering around in the dark.
Since a campfire is critical to getting through the opening hours of a survival game, most games make it a pretty simple task. Grab some sticks and some rocks. Craft a campfire in your inventory. Plop it down and turn it on. Now you've got a light source, a heat source, a basic kitchen, and a homing beacon.
