Capturing a moment is the essence of most of the photographic practices, but it's the documentary photography through which the social impact is most evident. The key element in documentary photography is presence of photographer at the scene and photographic „testimony“. From its very beginnings, this kind of photography strive to impact on society and human emotions, and its authors, encouraged by social engagement, hope that their photos will lead to some changes. Photography has found its place in documentary world because of its technical nature of creation. Its tight connection with the presentation of reality allows it multipurpose usage possibility. It is a informative content possibility, and in the same time its a medium for personal expression. In order to attract public attention, the contents of the documentary photography are usually shocking and interesting. If its to be any good at, it has to achieve the right balance between objective content and arbitrary subjective copyright act of creation. It is using all means in order to bring the reality of the observer. This thesis will explain documentary photography as an important form of photographic expression, with reference to the power and effect of its message. Also, it describes its development throughout history as well as the impact of technology, and its role in society today.