Take a look at the hello world template in the HOT directory in the same GitHub repository at https://github.com/openstack/heat-templates/blob/master/hot/hello_world.yaml.
The HOT format uses most of the same keywords that the AWS CloudFormation format uses. In the hello world template, you can see that almost all the same sections exist: heat_template_version, parameters, resources, and outputs. The configuration options for each of these sections look very similar; the main difference is that the HOT format is pure YAML and the AWS CloudFormation is a kind of YAML/JSON hybrid. The next step for us is to take these templates and launch a stack using them. We will use the HOT format to launch a stack next, so you will gain familiarity with this format in our practical application.