What it is
A digital signature proves that the holder of a private key authorised a message without revealing the key. Bitcoin originally used ECDSA signatures on the secp256k1 curve. BIP-340 standardises a different scheme, Schnorr signatures, on the same curve, so existing key types can be reused with a cleaner signature design.
Key specifics
BIP-340 uses x-only public keys, 32 bytes long, and produces signatures of 64 bytes. Verification is a short equation that holds only if the signer used the matching private key. The specification also defines how to generate nonces safely, because reusing or leaking a nonce in any signature scheme can expose the private key.
Why people care
Schnorr signatures are linear, which means several signatures or keys can be combined mathematically. That enables schemes where a group of signers produces one signature that looks like any other, which can save space and improve privacy for multi-party arrangements. The scheme also supports batch verification, so nodes can check many signatures faster together than one at a time.
What it means for you
You will not choose Schnorr yourself. Wallets use whatever signature type a coin and address type require. Bitcoin's newer address types can use BIP-340 signatures, while many other chains, including those in the Scrypt family, continue to use ECDSA unless they adopt the upgrade. If a wallet offers address types with names like Taproot, Schnorr signatures are part of how they work.
Why a new scheme at all
The appeal is not that old signatures were broken. It is that a linear scheme lets future protocols combine many signers into one compact, ordinary-looking signature, which reduces on-chain data and reveals less about how coins are controlled.