The process of redistricting is federally mandated every 10 years after the census comes out.  The purpose is to create 435 congressional districts that all roughly represent equal number of voters, and the redistricting is to create demographically balanced districts.  In theory this process will be politically neutral and all voters will have .

To understand this process better, let’s look more closely at how we should dividearagraph #2

This is that additional link mentioned in the video that shows a proposal as to how the the government can mathematically redistrict (and thereby avoid any intentional bias).  Unfortunately, a knowledge of place and regions is critical to forming workable districts and these perfectly straight lines are especially jarring in major metropolitan areas.