Unity's Multiplayer is a feature within the Unity game development platform that allows developers to create online multiplayer experiences. It provides tools and services for connecting players, managing game sessions, and synchronizing game states across different devices. This enables developers to build games where players can interact in real-time, enhancing the gaming experience. The system supports various networking models, including client-server and peer-to-peer architectures. With Unity's Multiplayer, developers can easily implement features like matchmaking, player authentication, and data synchronization, making it simpler to create engaging multiplayer games for various platforms.