Among its many different qualities, aluminum foil is also great for reflecting light. This means that you can reliably use it to better light your photos. Think of it like a professional reflector, only cheaper. A large piece of foil can be used to effectively reflect and disperse light for better conditions when photographing your subject. While you might only need a single sheet for small subjects, larger ones might require that you tape multiple sheets together.
However, this is certainly a cheap and quick solution if you ever find yourself in need of better lighting. Aluminum foil is common enough to be found near just about any shoot.