ECDSA (Elliptic Curve Digital Signature Algorithm) is a cryptographic method used to verify the authenticity and integrity of digital messages or transactions. By leveraging the mathematical properties of elliptic curves, ECDSA allows users to create digital signatures that are secure and efficient, even with shorter keys compared to other algorithms. It is widely used in cryptocurrencies like Bitcoin to ensure that only the rightful owner of a digital wallet can authorize transactions, providing a crucial layer of security for online communications and financial systems.