Thanks for bringing it up, Dave.

Lightning Network is integrated natively into Nostr. Along with setting a profile picture and a description, you can also set a few more fields in your nostr profile.

One of such fields is a LNURL. Its called lightning URL. Some wallets like Wallet of Satoshi, Bitcoin Beach Wallet, etc., support LNURL which you can attach to your profile. And once you do that anyone can send you Bitcoin(and sats) to your lightning wallet address.

And by tapping the lightning icon below every note(tweet), you can send zaps to others as well.

Why was Nostr built? You can find that in the article above written by the founder of Nostr.

Tldr: Nostr is the epitome of a decentralized social media. #[5] one day woke up and thought about how a decentralized social media would look like and was surprised nobody had thought of such an obvious model. So he laid the tracks to build what we now know and love as Nostr. He has got tons of support from the early adoptors and builders to achieve his vision along the way.