I learnt a lot at school, 99% I’m sure I can’t remember but somethings have stuck.
One of my most inspirational teachers at school once told me that “you can’t fully understand something until you can confidently articulate it”. He nailed it.
I’m not sure if someone had said that to him before or he just made it up there and then to make me revise harder, but he was right all the same.
Being able to explain a problem is understanding it, because if you can do that you can analysis it, break it down and solve it.