A multisig is a type of digital wallet or smart contract that requires multiple cryptographic signatures to authorize a transaction, rather than just one.
Here's how it works: Instead of a single private key controlling funds, a multisig wallet is set up with multiple keys held by different parties. To spend funds or execute transactions, a predetermined number of those key holders must sign off on it. This is often expressed as "M-of-N" - for example, a 2-of-3 multisig requires 2 signatures out of 3 possible signers.
Ref - https://github.com/solana-labs/solana-program-library/blob/master/governance/README.md
UI - https://github.com/Mythic-Project/governance-ui
Multisig implementation 2 - https://github.com/Cordelia-Program/Cordelia-Anchor
Not really. Platforms like tiplink allow users to eject out of the platform and own a single private key that they can independently keep/import in phantom/use to sign txns.
A multisig doesn’t have a normal account on chain. It has a program account/program data account.