EC2 is a service within AWS that allows us to run virtual machine instances. It allows us to control the type of operating system and set the amount of the instance CPU count, memory, and disk attached to the instances. Some instance types come with an instance store, which is included in the instance price, while others only support EBS. The EBS subsystem lets us create volumes that can survive instance life cycles and a loss of an instance and can be detached and attached arbitrarily to one instance at a time. To determine the availability zone and networking configuration, we put the instance into the VPC and select a subnet. When we have special requirements, an ENI can be used to persist the networking information independently of the instance. High availability should be configured for EC2 instances when required and placement groups can be used in special circumstances when we need to control how the cluster is placed. We also learned how to start an EC2 instance from the console. In next chapter, we'll handle server traffic with ELB.