This function follows the general equation for the slope-intercept formula:
y = mx + b
m is the slope, which is how much the graph move up whenever to move to the right by 1. In our case, our slope is m=2, so every time we move right by 1, we have to move up by 2.
b is the y-intercept. it's basically the starting point when x is 0. In our case, b=1 so we start at (0, 1)