ZeroTier is a software-defined networking solution that allows users to create secure, private networks over the internet. It enables devices to connect as if they were on the same local network, regardless of their physical location. This is useful for remote work, gaming, and connecting IoT devices. The platform is easy to set up and works across various operating systems, including Windows, macOS, Linux, and Android. With ZeroTier, users can manage their networks through a web interface, making it accessible for both technical and non-technical users.