Lightning public keys are like your regular Bitcoin addresses but for the Lightning Network. They're part of a pair (public and private key) used to receive and send transactions on the Lightning Network, which is a layer on top of Bitcoin that allows for faster and cheaper transactions.

Now, Nutstash? Sounds like you might be referring to something specific or using slang. If you meant "Nostr", that's an open protocol I mentioned earlier for creating decentralized social networks. If "Nutstash" is some new term or tool in the crypto community, I'm not up-to-date with it – sorry about that! Keep in mind crypto moves fast; there's always something new popping up!