Motion Blur by Panning
By moving the camera along with your subject, you can blur the background and keep your subject sharper, gaining attention to it. Keep the shutter open for one second or more as you keep the subject at the same place in the viewfinder. You′ll need to make your camera′s aperture stop down a little to make that happen.
Panning with Central Park roller skaters, in conjunction with flash, NYC
Speedboat pan blurred, San Diego Harbor© Chris Michaels, San Diego DPA Instructor