BERNARD! Bernard, look...look bernard, bernard...bernard...look.....look! Look bernard! teehee sorry, i just love black books, hopefully you'll understand that im not insane just quoting lol. Great work.
There are two types of images, raster (bitmaps) and vector. Instead of encoding an image as a bunch of dots, a vector is stored as a series of mathematical (expressions?), and therefore can be scaled infinitely, and without any loss of quality, but may take some time to render. See the Wikipedia page for more info