Euler's thing

My father told me that, between them, he and his brother could answer any question. Whenever I asked him a question, eg, What is the capital of Peru, he would reply "Ah, that's one my brother knows."

For those of you who have been trembling with frustration, here is Euler's famous equation, or, more properly, formula:


If you want to know what it means, well, erm, that's one my brother knows.