With zero knowledge of statistics, here's how to think about it - Wilson wants to construct some score. That score can be as low as 0 and as high as 1. So he wa

With zero knowledge of statistics, here's how to think about it - Wilson wants to construct some score. That score can be as low as 0 and as high as 1. So he wants some interval [x,y]. The center of that interval would obviously be c = (x+y)/2. Wilson first decides what c to pick. So Wilson says, the center c must be decided by the proportion of upvotes. But then he thinks, c must also be close to a half. So he says, okay, lets figure out c using some sort of an average. So he chooses two weights a and b. The weighted average would then be a times half plus b times the upvote proportion. He chooses those weights in such a fashion that if you have lots of data, one of the weights vanish & the other becomes unity. So the weights matter only if you have too few upvotes & downvotes. Having figured out the midpoint c, Wilson has to actually figure out the lower bound x and upper bound y. Now he draws a distribution centered at c....ok so at this point you would need to know what is a distribution, and why you would need one, whether that distribution has a skew & whether its homoskedastic & so on...which is stats 101, so I won't go there. But if you've gotten this far, you should be able to atleast see the intuition behind Wilson's procedure.