AWS CloudFormation StackSets extend the functionality of stacks by enabling you to create, update, or delete stacks across multiple AWS accounts and Regions with a single operation. We are now announcing the support for CloudFormation Macros and transforms in templates that are used to create a stack set. AWS CloudFormation macros perform custom processing on CloudFormation templates from simple actions such as find-and-replace, to helping CloudFormation Macros use the same technology that powers transform the entire template.AWS::Include and AWS::Serverless transforms. CloudFormation transforms help simplify template authoring by condensing the expression of AWS infrastructure as code and enabling reuse of template components.
Source:: Amazon AWS