When VPN network traffic is routing only some traffic over the secure VPN while other traffic directly accesses the Internet, what technology is being used?

split tunneling

Explanation:

Based on the information provided within the question it can be said that in this scenario the type of technology being used is known as split tunneling. Like mentioned in the question this refers to when a user is able to access different security domains such as a public network and a WAN at the same time. This can either be done with the same or different network connections.