Explanation
You can think of a Dynamic Routing Gateway (DRG) as a virtual router that provides a path for private traffic (that is, traffic that uses private IPv4 addresses) between your VCN and networks outside the VCN's region.
For example, if you use an IPSec VPN or Oracle Cloud Infrastructure FastConnect (or both) to connect your on-premises network to your VCN, that private IPv4 address traffic goes through a DRG that you create and attach to your VCN. For scenarios for using a DRG to connect a VCN to your on-premises network, see Networking Scenarios. For important details about routing to your on-premises network, see Routing Details for Connections to Your On-Premises Network.
Also, if you decide to peer your VCN with a VCN in another region, your VCN's DRG routes traffic to the other VCN over a private backbone that connects the regions (without traffic traversing the internet). For information about connecting VCNs in different regions, see Remote VCN Peering (Across Regions).