A camera obscura is a simple device that demonstrates how light can create images. It consists of a dark room or box with a small hole on one side. When light passes through this hole, it projects an inverted image of the outside scene onto the opposite wall. This phenomenon occurs because light travels in straight lines, allowing the image to be captured in real-time. Historically, the camera obscura has been used by artists like Leonardo da Vinci to help with perspective and composition in their paintings. It laid the groundwork for the development of modern photography and cameras, showcasing the fascinating relationship between light and image creation.