Natural sources of light include sunlight, the stars, volcanoes, meteorological lightning and biochemical sources. These types of light are naturally occurring and do not necessarily need humans to create light.
Sunlight is one of the most obvious and prominent sources of natural light for humans. It is constantly present in the Earth and provides a large amount of light for people to see by on a daily basis. It is also the largest source of light available to humans. Starlight is similar to sunlight in that it comes from stars that are within the galaxy and beyond, although these stars are much smaller and further away than the sun. Lightning also exists in the atmosphere under ideal conditions and is able to provide a small source of light for the people who live on earth to use. It is generally a quick flash of light.
Due to the high temperature of the volcanic materials within a volcano, it is able to light up and provide a source of light for humans. This light is extremely hot and is not a good source of light on an everyday basis. An example of biochemical light on the Earth would be lightning bugs or fireflies and jellyfish who emanate their own light sources from places within their bodies.