The math vectors have EVERYTHING to do with Vector Graphics! In a Vector Graphics environment (for example, I use Corel Draw!), every item is specified as a particular type of mathematical entity, such as a straight line, a circle, an ellipse, a Bezier curve, etc. Each type of graphic element has a small number of parameters that completely define it in space. For example, a straight line in 3D space is defined by its start point (x1, y1, z1) and its end point (x2, y2, z2). Those six parameters, plus the note that the element is a straight line, are all that is needed. Each of the six parameters can be a floating-point number of any precision the software uses. Complex things like Bezier curves have more parameters to define them, but still a modest number.
Now, how do we see those things? On a computer screen the picture is ALWAYS a bitmap graphic. That is, the screen is divided into a finite number of pixel locations (say, 1680 across x 1050 down), each with three possible colors (usually red, green and blue), and each of the colors having a possible finite number of brightness levels (typically 256). When Vector Graphics software is told to display the picture it has with all its vector elements, the first thing it does is check how the screen is set up and compare that to the zoom level the user is using and the point of view. Then it uses the vector equations for each element, plugging in the particular parameters for each one, and reduces the information to exactly which pixels should be turned on (and to what brightness level) to represent the vectors within the viewing area. That info, pixel by pixel, is fed to the RAM of the video card so you can see it on your monitor. This is all done by the rendering engine part of the software. If you change the area you want to see, or the zoom factor, it all gets re-done to fit. If you zoom in enormously, the precision of the vector math calculations means the curves etc. will still look smooth because the fine detail can be calculated and displayed. You can re-scale to your heart's content, because that just means multiplying every graphic element's parameters by a constant or two to get new parameters.
In bitmap graphics drawings, all the elements of the picture are simply the exact specifications for which pixels are turned on, and to what brightness, for ONE fixed picture dimension. There is no knowledge of shapes of sizes, nor any relationships to what is being represented by the pixels. A digital photograph is a good example of one of these. If you zoom in on a part of it, all the display system can do is make bigger blocks of the same color to represent one pixel in the drawing by, say, a block of 100 x 100 pixels if you zoomed in by a factor of 100. You can't really re-scale anything very well.