The Java Secure Socket Extension (JSSE) is a set of packages that enable secure Internet communications in Java applications. It provides a framework for implementing secure socket communication using protocols like SSL (Secure Sockets Layer) and TLS (Transport Layer Security). JSSE allows developers to create secure connections by encrypting data transmitted over networks, ensuring confidentiality and integrity. JSSE supports various cryptographic algorithms and key management techniques, making it flexible for different security needs. It also includes features for authentication, allowing clients and servers to verify each other's identities. Overall, JSSE is essential for building secure Java applications that communicate over the Internet.