Virtually all SLRs offer a choice of different modes of use depending on the image you are planning on capturing. Thus, a clear distinction can be made between an automatic mode, a series of predefined modes and manual or semi-manual modes. The preset modes are programmed for use in a number of specific circumstances that the manual usually helps to define.
The manual or semi-manual modes are for full control of the camera. Of course, they are also the most complicated to use but can potentially provide you with the best quality photos. In order to use these modes correctly, it is necessary to master at least some basic photography concepts. Remember that it is in manual mode that you can capture the most impressive photos.