Here is the website I got the image from. They have a page on performing your own star-trail photography
here, for those interested.
The basic idea is really quite simple. As the earth spins, the stars remain fixed, so from a given point of the earth, the stars appear to rotate about a point directly above the axis of the earth, exactly as if you painted stars on your ceiling and spun in a swivel chair. Of course, the stars only rotate as quickly as the earth does, so only about 15 degrees per hour - far too slowly to notice when just looking up at the sky. Images like this one are produced by pointing a camera at the sky and exposing the film in it over a several hour period. As the stars move, they leave trails on the film everywhere they have been over the course of the exposure, just like you can get a blurred image of a fast-moving subject when taking a regular picture. Because the exposure is so long, you get a record of every point the star visits while the camera shutter is open.
Of course, you don't need a camera to locate a pole star - ancient mariners used celestial navigation over two millenia before the invention of film by determining the location of the north star. You could locate it with careful observation over the course of a single night if you were determined. Photography just makes the process trivial and provides convincing and beautiful images of the phenomenon.