We receive the visual world in minute glimpses, transmitted and recorded by impulses of light on our retinal surface and then as electronic stimuli to our brain. Our brain continues to process the virtual stream of imagery, allowing only a fraction of a second for identification and assimilation of each image into meaningful information. 
To continue to process the images we receive, we must rely on memory, or rather, our ability to hold an image as visual thought. In similar fashion, photographs are records of equally short durations of light chemically retained on sensitized surfaces, yet they are durable and available for prolonged scrutiny; details and context are infinitely reviewable. What could be a better system for better understanding, perpetuating or extending our brief view of the real world? 
Despite the simplicity of the above comparison, the actual differences between sight and photography is anything but simple. And instead of nominally expanding our ability to better see the world, we instead struggle to grasp the barrage of imagery that photography permits and fosters in our modern culture. 
We see more images than ever before; our visual world grows daily with images designed to grab our attention amongst a daily display of competing visuals. To compound the difficulty further, images are also attached to differing meanings through their contextual delivery. The media surrounding the embedded image often redirects our understanding of already complex subject matter.