Im learning BIT (Fenwick tree), i saw a expression that is x & -x to find largest power of two don't larger than x.

But i can't clear this expression, please tell me the truth. Thank you very much!

I asked GPT but it have just give example but don't proof. I've just known that this expression is a trick :'( and no more.

And more, could you give me some bitwise-research-documents? I hope that learn more about bitwise, thank you.