Holy fuck, I thought maybe there was an epic conversation today, but it turns out it was just Jocke having a tourettes attack. Thank Oden for that actually, fuck actually reading that many pages
Rasterizing something is basically turning it from a "shape" (vertex) into a flat image. Like if you used Corel Draw and made a triangle you can then edit it freely, but to finalize and flatten it with the rest of the image you have to "rasterize" it and then you can't play with it anymore (not on the vertex level).
Yay now you can be more confused! I keep myself in a constant state of confusion.