Note: This is what I found on quiver documentation from https://matplotlib.org/3.1.1/api/_as_gen/matplotlib.axes.Axes.quiver.html
(I am trying to understand it myself : )
Here origin of vector is (x, y) = (0, 0) and head is (u, v) = (3, 4)
Apparently, there are multiple options to specify the units and scale_units ranging in values from ‘inches’, ‘dots’, etc etc.
If you look up scale_units meaning, there is a line which says:
To plot vectors in the x-y plane, with u and v having the same units as x and y, use
angles='xy', scale_units='xy', scale=1 .