Cloud Formation is a service which is provided by the AWS to model and set up the resources, so you can spend more time on your application and less time on managing this resources.
We can create a template using the cloud formation designer, where you will specify the all the resources needed (EC2, S3, SES, etc) and dependency between them, such that we can create a template using this design.
These templates make the work easy for the developer as each time he doesn't need to configure or set up the resources and it save a lot of time for them as they can get all the resources configured within few clicks of the button.
The major advantage of using this is that you can even provision and mointoring all the resources using it.