It's a classic but still relevant flow chart.

What do hexagons and octagons mean in a flow chart?

I think in this case, probably nothing other than they draw attention to whatever you're supposed to see as most prominent because they're a different shape. But there's a handy dandy flow chart shape explanation here (sadly, no octagons or hexagons included): http://www.rff.com/flowchart_shapes.htm