light painting photography

Have just stumbled across this genre almost by chance while researching something else. At the moment I don't completely understand how it's done - a combination of moving light and slow exposure? - but it's as if movement and time are frozen into a single image eg.

Gijon Mili, Picasso Paints a Centaur

or illusory structures created out of light e.g.

Eric Staller, Ribbon on Hannover Street 1976

http://lightpaintingphotography.com/light-painting-history/