The compute classic documentation will explain all these concepts and how to work with them. There is a chapter on IP Netwroks in prticular - https://docs.oracle.com/en/cloud/iaas/compute-iaas-cloud/stcsg/configuring-ip-networks.html
Thank you Chris, but the document doesn't explain how to setup security rules for those nat's ip's
Actually I have and instance with both ip's and I just can access ssh to the public ip. I don't know if there is a document that explains how to open ports to the nat's ip's
So you have access to the public IP. Are you asking where/how you add rules to allow you to ssh from your client directly to the VM using its private IP? When you say 'NAT IP' are you referring to the private IP?