Wintun acts as a Layer 3 virtual adapter that allows user-space applications such as VPN software to directly work with IP packets. It functions as a TUN interface, creating a virtual network adapter that provides direct access to network layer (IP) packets through simple file read and write operations. Much like a physical network card, it supports assigning IP addresses, configuring routes, and transmitting data. The key difference is that, unlike real hardware, all packet transmission and handling are managed entirely by user-defined programs in user space.