Hello,

Is anyone able to explain in clear terms, maybe with a simple high school level formula, what difficulty is and what it means exactly for mining?

Apparently it's a measure of how "difficult" it is to find a block below a certain target, which adjusts every 2016 blocks. But still, with the current difficulty of 5814661935891.805 as I write this, I don't know how to interpret this number.

Difficulty is the number of shares required to find a block at a perfect luck of 100%. Luck is rarely exactly 100% though.