How exactly is the font Computer Moder stored on my hard drive?
I know that Computer Modern was designed using METAFONT and that METAFONT only outputs bitmaps. So does my hard drive actually just contains the geometric description of the font, and whenever TeX is executed it calls METAFONT to generate the bitmaps needed for this specific source file? Does it generate the font on each execution again? Does this mean that my final PDF contains a bitmap for each symbol I used in each variation (larger, bold, italic, ...) in a pretty high resolution (zooming in using Acrobat Reader has not shown any pixelation)?
If it is not the case that the font is always generated "on the fly", how can such an easy customization of Computer Modern be possible as demonstrated e.g. here.