AWS Certified Solutions Architect Associate Test 5

A stack is a collection of AWS resources that you can manage as a single unit. In other words, you cancreate, update, or delete a collection of resources by creating, updating, or deleting stacks. All theresources in a stack are defined by the stack's AWS CloudFormation template. A stack, for instance,can include all the resources required to run a web application, such as a web server, a database, andnetworking rules. If you no longer require that web application, you can simply delete the stack, andall of its related resources are deleted.

You are charged for the stack resources for the time they were operating (even if you deleted thestack right away).
Reference: http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/stacks.html