A service that connects an on-premises network or another cloud to a VPC through encrypted IPsec tunnels over the internet. HA VPN, with two tunnels to the remote device, offers a 99.99% SLA.
On the ACE it is chosen for encrypted hybrid connectivity over the internet, with modest volume or quick setup. For high private bandwidth you use Cloud Interconnect.
Cloud VPN (HA VPN) is a concept that can show up on the exam. Check the full guide to see it in context.