Onion over VPN is an essential feature offered by several VPN providers that allow users to access the secure and private Tor network through their VPN connection.
The Tor network is free and open-source software, enabling users to browse the Internet anonymously by routing their traffic through a series of relays, making it almost impossible to trace their online activity back to their original IP address.
When Onion goes on top of their VPN encryption — when users first connect to a VPN server before accessing the Tor network — an additional layer of security and privacy is added. By routing the traffic through the VPN server first, the internet service provider (ISP) or network administrator won't be able to see if users are accessing the Tor network.
This feature is useful to individuals looking to maximize their anonymity and privacy online, like journalists, activists, or individuals living under repressive regimes. However, it is important to note that using Tor and VPN together may result in slower connection speeds (sometimes unbearable) due to the additional encryption and routing.