effectual reasoning is taking stock of where you are, and seeing where you can get to from there. causal reasoning is looking at where you want to go, and working backwards to connect the dots.

An example from CommonCog's article, when action beats prediction

If you use causal thinking, you’ll say something like “ok, we’re making carbonara tonight” and then you will work backwards from the end goal (carbonara for, say, five people) to checking for ingredients in your kitchen, to purchasing the ingredients you don’t have, to prepping and cooking carbonara for your dinner party.

If you use effectual thinking, you’ll say something like “ok, what ingredients and tools do I have right now, and what can I make tonight?” You work forwards from existing resources; the end product is unknown.