Stopping: You can stop an EC2 instance and stopping an instance means shutting down the instance. Its corresponding EBS volume is still attached to an EC2 instance, so you can restart the instance as well.
Terminating: You can also terminate the EC2 instance and terminating an instance means you are removing the instance from your AWS account. When you terminate an instance, then its corresponding EBS is also removed. Due to this reason, you cannot restart the EC2 instance.