When you activate a VPN key share app, it essentially intercepts the internet traffic from any device connected to the host device (via hotspot or proxy). This intercepted traffic is then routed through the host device's already established VPN tunnel. The VPN app on the host device encrypts this combined traffic and sends it to the VPN server. When the VPN server sends data back, it goes to the host device, which then decrypts it and forwards it to the intended connected device