When shooting photos in shutter speed mode, you control the camera's shutter speed, while your camera selects the appropriate aperture in order to get the proper exposure. Photographers would often shoot in shutter speed mode when covering sports, because they want to freeze the action.
While I've known about shutter speed mode and its uses for quite some time, I never used it very much. The reason is that depending on the lighting conditions, the camera may not find an aperture long enough to properly expose your photo at the shutter speed you desire. This can lead to underexposed images, sometimes severely underexposed. Instead of shooting in shutter speed mode, I would shoot in aperture mode. I would often shoot at the largest aperture, reasoning that a shutter speed faster than I desired would not hurt when trying to freeze the action. If I found that I couldn't get the desired shutter speed at the largest aperture, I would increase the ISO settings. Increasing the ISO makes the camera's sensor more sensitive to light (at the expensive of noise in the photo), which allows you to shoot with faster shutter speeds.
Another feature that I never really made use of was the Auto ISO feature of my camera. My Canon 40D had an automatic ISO feature, but its range was 400-1600. I found that when I used an ISO of 800 or higher, the images from the 40D had too much noise. Since the actual usable range was so limited, I never used the Auto ISO setting on the 40D.
Although my Canon ID Mark IV and Canon 5D Mark II handle noise much better than my 40D, I never really used the Auto ISO feature with them either. This was really a bad idea on my part, because not only do the camera's show much less noise at the lower ISO's, they also have a much larger range of ISO's covered by the Auto ISO setting.
When I went to shoot some of the BBSA baseball games today, I decided to set my camera to shutter speed mode (TV on Canon) and select the ISO to auto. By doing this, I could control the camera's shutter speed, ensuring that I could freeze the action, and the camera would pick an appropriate aperture and ISO to get the correct exposure. I was very happy with the results. Instead of having to worry about changing the ISO when the lighting might change, the camera did it for me. I was very pleased with the results. I need to do some research, however, to understand better how it balances between the aperture and ISO.
Next time I am going to try to shoot in manual mode with the auto ISO set. This would give me control of both shutter speed and aperture, with the only setting picked by the camera the ISO.
Recently, I've also gone back to shooting outdoor sports in JPEG mode. This is one of the times where the advantages of RAW are outweighed by the faster frames per second and smaller space taken on the hard drive. The only downside is that I need to make sure I change the settings back when shooting something else.