Photography is a combination of two words. PHOTO and GRAPHY. Photo is a Greek word for light, light not in the sense of heavy or light but light as in the sun. Graphy means something along the lines of drawing. Putting these two words together would mean "drawing with light".
Photography can be seen as the process of recording images on sensitized material by the action of light, x-rays, etc. It is also the chemical processing of this sensitized material to produce a print or a slide. Basically, light+film = photography.
People use photography as an art to capture or record moments or events so the memory will not be lost, as a commercial activity mostly done with a customer in mind, as a documentary which entails making a story about something with captured images to add more spice to the story and also to make public record.
Photography is an amazing way of capturing moments. It helps to save memories and relive happenings all around the world. One can only imagine what our lives would be like without photography.