How does having a shared IP address help?
When you use a VPN to browse online, the VPN creates an encrypted tunnel between your device and the internet. The VPN masks your IP address and shares it own as part of the connection process. The Server IP Address is shared with every person who is currently using that server which means that any traces can only be traced to the server and cannot be used to identify the end use.
By using a VPN, your own IP address is obfuscated by the VPN connection which protects your personal information and activity from anyone who wishes to monitor you.