In AWS, what is the difference between rebooting and stopping/starting an EC2 instance? Explain it in terms of what happens in each case when dealing with a EBS Volume vs Instance Store volume (i.e. EC2 is created from Instacne Store AMI where you have no visibility to the volume from the AWS console)?

Rebooting, just reboots the underlying OS, whereas Stop/Start, is done when there is something wrong with the underlying Host hypervisor. Stopping and instance and starting it, could cause the instance to run on another host (i.e. could result in new IP, etc). So in case of EBS Volumes, nothing bad happens (as new instance running on possible new host just gets attached to same EBS volume), but if you have EC2 backed by Instace Store AMI, Stop/Start will kill/delete/wipe the root device volume.

^^ note that when you stop an instance, you don't get charged for compute anymore, but if you are using an EBS backed volume, you do get small storage charges for the EBS volume.