A Unix domain socket is a local inter-process communication (IPC) endpoint used by programs on the same machine to send data to each other. Unlike a TCP socket, it does not use the network stack or a remote IP address; communication stays on the host and is usually controlled by filesystem permissions.
Security-wise, Unix domain sockets matter because they often connect unprivileged applications to privileged helper services. That makes them a common trust boundary in macOS and Linux software. If a root service accepts attacker-controlled messages over a local socket, a low-privilege user or malicious local process may be able to trigger sensitive actions, leak data, or reach command execution. Defenders should treat local IPC endpoints like any other attack surface: restrict access, validate message contents, and avoid passing socket input into shell commands or unsafe parsers.