Schnorr signatures are a modern type of digital signature scheme that is used in cryptography and blockchain technology. They are a way of creating a digital signature that is more efficient, secure, and flexible than other signature schemes. Schnorr signatures are based on a mathematical problem known as the Schnorr discrete logarithm problem, which is believed to be hard to solve. This makes them suitable for use in cryptographic systems, where they can be used to create digital signatures that are difficult to forge. Schnorr signatures have been proposed as an upgrade to the existing digital signature scheme used in Bitcoin, and they are also used in other cryptocurrencies and blockchain applications. Schnorr signatures provide the ability to merge multiple transactions, extending Bitcoin's capabilities and efficiency.