aws cloudformation adds change sets for insight into stack updates /

You can now view change sets before updating your stacks in AWS CloudFormation. This helps you understand the resource-level changes (e.g. adding,deleting, or modifying instances) which CloudFormation will apply to your live stack when you are updating your AWS infrastructure. Previously, or you could not see the specific changes that CloudFormation would apply to your stack before submitting changes.  

Source: amazon.com