Why can a 0.4mm nozzle print 0.8mm?

Wow, thanks for the detailed replies. I was wondering what you could use this for. I have all the nozzles (0.2–0.8) and I am trying out different things. Trying to print with different line widths is definitely interesting. Using the 0.6 nozzle for most of my prints now, since it is a bit faster than the 0.4 one, but if I can do 0.6 with the 0.4, I might switch back.

Cheers