TLDR Signet lets you sign anyones NFT like an autograph on it, and then layers them all so you can collect signatures from various addresses fully onchain/through IPFS. So like each NFT has a mapping where all signatures are stored, then the dapp layers all the signatures and renders it.

This also allows these to be soulbound to the NFT much like real items that are signed. This may seem a little simple but both allows for it to be done for all NFTs so large market with easy to understand use case and even built in a system where you can optionally put in a bounty bid for someone to sign your NFT for the bounty from a specific address, so influencers/notables/creators can earn directly for signing peoples stuff.

Also because its all onchain you get like guaranteed provenance and that. Uses ENS even on testnets and other chains to make the UX cleaner and provider better authentication.

(Note, yes I build a lot, would prefer the grant going to this vs tag the wall but its newer so not as polished)