Cryptography is a science about keeping information secure.
It transforms a message into a format that cannot be read by unintended recipients.
Julius Caesar was one of the first people to use cryptography. He wrote private correspondence with some letters scrambled. In order to read the correspondence, you’d need to know an algorithm to decode the words. For example, every “e” might be swapped for an “a”.
The techniques used in cryptocurrency are more sophisticated than Caesars and have some added functions. Bitcoin uses hashing to verify integrity of data, digital signatures to ensure identity and public/private keys to securely encrypt and decrypt data.
Cryptography keeps the network and your currency secure.