A Site-to-Site VPN is a secure connection between two or more networks over the internet. It allows different office locations or branches of a company to communicate as if they were on the same local network. This is achieved by encrypting data transmitted between the sites, ensuring privacy and security. Typically, a VPN gateway is set up at each location to manage the connection. This setup is beneficial for businesses that need to share resources, such as files and applications, across multiple sites while maintaining a high level of security and control over their data.