The SVG viewBox is a whole lot of magic rolled up in one little attribute. It's the final piece that makes vector graphics Scalable Vector Graphics. The viewBox does many things: It defines the aspect ratio of the image. It defines how all the lengths and coordinates used inside the SVG should be scaled to fit the total space available. It defines the origin of the SVG coordinate system, the point where x=0 and y=0.
transform="translate" can transclate by px only, use <use> to translate by em