Within the same template, you can use the Ref intrinsic function to specify the parameter value in other parts of the template. The following snippet uses the the previous defined parameter InstanceTypeParameter:
Ec2Instance: Type: AWS::EC2::Instance Properties: InstanceType: Ref: InstanceTypeParameter ImageId: ami-3c47a355
There are some AWS-specific parameter types as well. For example, if you mention AWS::EC2::AvailabilityZone::Name, then the value of current AZ such as us-east-1 will be placed in the CloudFormation template. Similarly, there are many more AWS-specific parameters that exist.
Mapping (optional): The mapping section which is also optional, matches a key to a corresponding set of named values. Let's say ...
