Photography is defined as "the art or process of producing images by the action of radiant energy and especially light on a sensitive surface (as film or a CCD chip)." The most common media are film and electronic sensor. During a timed exposure, a controlled amount of light is captured by a camera, which stores the information on the media for further processing.
Once the image is recorded, it can then be processed. For film this is a chemical process; for digital media, one can use an image-processing application like Adobe Lightroom. From there, the image can then be printed, or uploaded to the Internet onto photo-sharing sites, or displayed in other ways.
Photography can be a hobby, or practiced at the professional level. It is used for portraiture, advertising, illustration, journalistic efforts, fine art, and even in the science and technology fields. The transition in prominence from film to digital photography has been rapid. Taking place roughly from 1995 and 2005, the digital revolution happened much faster than anyone imagined.
While many of the techniques that were used in the days of Ansel Adams are still valid, with modern tools like Adobe Photoshop photographers have many more methods for working with images, as well as many more opportunities for manipulation, and even dishonesty. What photography will be like in another hundred years is anyone's guess.