CloudFormation provides some UI screens to allow developers & release engineers to easily describe the makeup of their applications. Under the covers, the description is turned into a structured template. This template can then be sent to the AWS provisioning engine which understands the dependency chain - and launches each component in the precise order.
In standard AWS fashion, the template descriptions are available for developers to review or to create from scratch. Once a template is created, CloudFormation provides an API for developers to call which will take the template as input and execute it. It's great to see Amazon continue down the path of not only providing UI's but also making the functions available as services.
At MomentumSI, we've been anticipating the launch of this service. It pulls together all of the piece-parts which Amazon has been developing over the years. Finally, the picture can be painted on how Amazon can be used for complete application solutions. I tip my hat.