This is a fuse box. Every location will have one of these, and they may appear in different rooms each time.

In most difficulties, the fuse box will start off, and the light will be red. Click the red box in the bottom left with the left mouse button to toggle it on/off. If the light is green, the power is on.

When the power is on, several things happen. Electricity becomes available, meaning you can now interact with light switches with the same button to turn the lights in that room on. The temperature will also be affected, which is important when playing the game.

In most difficulties, the fuse box will start off. The power hasn't been on for a while and that means the entire location will be cold. Generally*, it is a good idea to keep that power on because the house will heat up. That means you can use a thermometer to find the ghost room quickly and efficiently. (We will go over the thermometer more in the Equipment chapter)

Light is your friend. Glowsticks and candles both light up a small portion around you, or you can turn on the light in the room. Staying in the light will keep your sanity from dropping. (We will go over sanity more in the Sanity Pills chapter) Using only a flashlight in the dark means you are in the dark - and when you're in the dark, your sanity will drain.

* There is a ghost called the Jinn that becomes more powerful if the fusebox is on. At the same time, the Mare is less active when the lights are on. It depends on what your ghost is.