People photograph to capture something. Whether it be a moment, an emotion, or a story, photos are taken to preserve that image. Photos are taken on many different occasions of all different subjects, but they are usually taken for this reason. For example, many families take pictures during certain holidays, such as a Christmas card. Usually, these serve to capture a time in you life. They show the people you don't see often, or even those you do, how much you have grown since the previous year. Although a Christmas card looks extremely different then a picture of the trees reflecting in a puddle after a rainstorm, they are bound together by their reason for being taken, capturing a moment.
There are several aspects of a photograph that can contribute to its success. In my mind, the most important thing about a picture is that it captures attention. Making it visually appealing is undoubtedly important, but there is more to a photo then simply the subject and composition. Personally, the photos that make me look twice are the ones that have an aspect of mystery. I like photos that really make you wonder what the photo is of, or why it was taken, or even how it was taken if, for example, it is at a very unconventional angle. The photos that capture a story are far more interesting to me than the ones that simply capture the beauty that lies on the outside, so I find those to be the most successful.