1 - Shutter speed is (normally) derived from a combination of available light, lens aperture and camera ISO setting.
2 - Slow shutter speeds are how one makes water blur or adds a "movement" feeling (also called "panning") to a photo.
But that's not all of course - now we have to hit the other end of the spectrum and shoot quickly!
If slow shutter speeds "melt" action, then fast shutter speeds freeze it. Fast shutter speeds are absolutely essential for many types of photography, which is why manufacturers pour so much time and energy into allowing their cameras to reach higher shutter speeds (by improving the ISO performance of their cameras). Below are a couple of fast shutter-speed scenarios.
ISO 360, f/8.0, 1/750s
ISO 100, f/2.0, 1/3200s
Fast shutter speeds are important for a great many types of photos, which is one reason why fast lenses (lenses able to open up to large apertures, like f/2.8, f/2.0 or even f/1.4) cost more than slower variants - even one stop of light (say, from a maximum of f/4 to f/2.8) can be worth $1000 or more - that extra stop lets a photographer get a shutter speed that's twice as fast as what the slower lens would allow.
It's also the reason manufacturers put forth a lot of effort in improving their cameras' ISO performance - the higher the ISO a photographer can shoot while still getting clean photos, the better.