A number that is generated from a private key using the Elliptic Curve Digital Signature Algorithm (or ECDSA).

A digital signature is used to prove that you own the private key associated with your public key and that you have authorized a transaction.

Digital signatures are verifiable by anyone who has access to the public key associated with the signer's private key using the same elliptic curve algorithm. 

Learn more about Why digital signatures are essential for blockchains.