VPNs are used to secure your connection on public Wi-Fi, allowing you to browse in complete privacy. Hackers have a variety of methods for stealing your data while using public WiFi, but with a VPN, your online traffic is invisible to them.
When you use a VPN to access Netflix, your region is concealed, and Netflix displays content that is available in all regions worldwide.
If you don't see content that you believe is available in your region, it could be because you're using a VPN. Turn off your VPN and re-access Netflix to ensure you're getting the same content catalogue every time.