Style may be defined as: A quality of imagination and individuality expressed in one's actions and tastes. I like to think of style as the signature of an individual that is expressed throughout their life daily. People, I feel, often confuse "fashion" with "style". Fashion, especially clothing, comes and goes and is dependent greatly on the particular culture/world view/profession/etc. that is popular at that time. Style transcends fashion in that it is timeless and exudes from the individual not the culture at large.
In addition to clothing, the term can be applied to a plethora of ideas and actions. There is a certain style that a chess player will develop and use when he learns to play the game well. There is an inherent style that a photographer will eventually develop in regards to perspective or editing, even if unbeknownst to themselves, if they are consistent with their shooting over time. "Fashion", in this sense, would be congruous to using a en vogue/popular opening during a chess match or using a popular photographic editing technique that is trendy for the year (yes, you're right... I'm not an HDR fan! :))
When a person comes to a realization and understanding of their style and the manner in which they approach things, they are that much closer on the long path of self-discovery and improvement.