IAM Group is A collection of users who all need the same type of access to a particular set of resources or compartment.
IAM DYNAMIC GROUP is A special type of group that contains resources (such as compute instances) that match rules that you define (thus the membership can change dynamically as matching resources are created or deleted). These instances act as "principal" actors and can make API calls to services according to policies that you write for the dynamic group.
Reference:
https://docs.cloud.oracle.com/en-us/iaas/Content/Identity/Concepts/overview.htm GROUP:
A collection of users who all need the same type of access to a particular set of resources or compartment.

Oracle Cloud Infrastructure Container Engine for Kubernetes is a fully-managed, scalable, and highly available service that you can use to deploy your containerized applications to the cloud. Use Container Engine for Kubernetes (sometimes abbreviated to just OKE) when your development team wants to reliably build, deploy, and manage cloud-native applications. You specify the compute resources that your applications require, and Container Engine for Kubernetes provisions them on Oracle Cloud Infrastructure in an existing OCI tenancy.
You can access Container Engine for Kubernetes to define and create Kubernetes clusters using the Console and the REST API. You can access the clusters you create using the Kubernetes command line (kubectl), the Kubernetes Dashboard, and the Kubernetes API.
Container Engine for Kubernetes is integrated with Oracle Cloud Infrastructure Identity and Access Management (IAM), which provides easy authentication with native Oracle Cloud Infrastructure identity functionality.

The Oracle Cloud Infrastructure Domain Name System (DNS) service lets you create and manage your DNS zones. You can create zones, add records to zones, and allow Oracle Cloud Infrastructure's edge network to handle your domain's DNS queries.

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).