Basic photography is using light to record an image onto a medium, such as paper or a computer display. It is thought that the ancient Romans possibly made contact prints of objects on paper that was coated with a mush of flower petals or grass or teas, then exposing this to the sun. No evidence exists of this process because the image fades and disappears over time. It was the early photographers Joseph Nicéphore Niépce, in the 1820's and William Henry Fox Talbot in the 1830's and 40's, who figured out how to fix the image onto a surface like metal plate or paper with a chemical solution so it wouldn't fade.
You can try this yourself by placing an opaque object, such as a leaf, flower, or some grass, onto a sheet of paper that has been painted with tea or coffee, lemon or orange juice. These are placed into a glass picture frame, then positioned in a sunny window towards the sun for a few minutes, hours, days, weeks, or months, depending on your emulsion sensitivity. When the exposure-development is done, take the paper and object out of the frame to see the result, your first photo! This ordinary process is what causes the fading of objects placed in sunny windows for months or years at a time. With photography, we control the sensitivity of the film, the time of exposure, the quality of development, and focus the image using a lens in a camera.
In traditional photography classes, these are called photograms, using a darkroom with black & white chemicals, and exposing B&W enlarging paper using room light or an enlarger lamp. Modern computer users can use a digital camera and computer to make a print onto paper at home or use a digital photo lab. An "Alternative Photographic Technique", is to make large negatives using inkjet printers with special transparency media (for OHP's). Sandwiched underneath a glass "contact printing frame" with printing out paper, exposed and developed using sunlight for a few minutes, then removed to be washed and fixed with ordinary B&W fixer chemical. This Printing Out Paper (POP) is still manufactured today.
Life vs photography
Many artists use photographs as reference material. But it is the opinion of most art teachers that, when one has the opportunity to use an actual object as the model for a work of art ("working from life"), to do so is vastly preferable to using a photograph.
Why is this? Simply because no matter how detailed or accurate the photo is, it can never contain all the information that is in the actual object.
A photograph can only show us what one photographer saw, from one angle, under one lighting condition, at one moment in time. A photograph of an object is not three-dimensional; it does not include the tactile sense of that object's weight or texture; it omits interesting details such as the sound the object makes when tapped, or its scent or taste; and, most importantly from a visual artist's perspective, the photographed object cannot be handled and turned about, taken into another room and examined under different lighting conditions, or dissected for further study.
The opportunity to completely examine an object is extremely valuable to the artist. Though the findings obtained through examination of the object may not seem to appear in the content of the artwork (for example, the artist may carefully examine a very red apple and still paint it in black ink), the knowledge gained from examination of the object will produce a richness in the artwork which would be lacking had the artist not examined the object.
Finally, even if the actual object cannot be moved, handled or taken apart, the opportunity to view it from several different angles will improve the artist's understanding of the object's construction.