Answer
HVM (known as Hardware Virtual Machine) is the type of instance that mimics bare-metal server setup which provides better hardware isolation. With this instance type, the OS can run directly on top of the Virtual Machine without additional configuration making it to look like it is running on a real physical server. For more information about this instance type and the other one that is most commonly used, you may refer to the resource link below.
Additional Information Here: http://docs.aws.amazon.com/AWSEC2/la...ion_types.html
