Public-Key Cryptography is a secure method of communication that uses two keys: a public key and a private key. The public key is shared openly, allowing anyone to encrypt messages intended for the key's owner. Only the owner, who keeps their private key secret, can decrypt these messages. This system ensures that sensitive information remains confidential, even if the public key is widely distributed. This technology is essential for online security, enabling safe transactions and communications over the internet. It underpins various applications, including SSL/TLS for secure web browsing and PGP for email encryption, protecting users' data from unauthorized access.