Shutter speed is a part of the exposure triangle and has a direct and profound impact on your images. In a nutshell, when you take a photo, the lens is letting light into the camera. The shutter is what opens up to let the light reach the sensor, then stops the light from reaching the sensor by closing. The speed at which this happens is usually incredibly fast. However, no matter how fast it is, it still impacts your image differently. Do you want star trails to appear in your image? Go with a very slow shutter speed, leaving the shutter open for multiple seconds/minutes. Do you want to freeze an action shot? Use a lightning fast shutter speed of 1/2000th of a second or higher. In the above photo, I did just that, resulting in a crisp picture, where the baseball appears frozen in time with the laces clearly visible.
If you don't fully understand the exposure triangle, and how shutter speed, aperture, and ISO impact the photo, it may be useful to shoot in Shutter priority mode. This is usually marked as an S or Tv on the camera dial. This lets you pick the shutter speed, while the camera sets everything else based upon the shutter speed you set. This works in most situations, but for more advanced shooting, using M- manual mode, lets you set all of the values for the specific look you want. An example of this would be in a poorly lit gymnasium, where the camera may not be able to adapt to a low enough aperture or high enough ISO to compensate for your shutter setting. In general, though, the Shutter priority mode will work for most instances.