AWS CloudFormation Templates are the basis for a CloudFormation stack. It is a JSON or YAML-formatted text file that describes the infrastructure resources needed and their dependencies. The template follows a specified schema, allowing users to specify resources, configurations, and mapping values. By using CloudFormation templates, you can automate, version, and reuse your AWS service configurations. This helps in managing and updating an infrastructure in a predictable and efficient manner.

A stack is a group of related resources provisioned by AWS CloudFormation based on the provided template. When you create, update, or delete a stack, CloudFormation automatically manages all the resources defined in the template file. Stacks can be created, updated, and deleted from templates uploaded to an S3 bucket, or directly from the AWS Management Console using the provided templates. Stack management becomes essential in efficiently deploying and maintaining complex, multi-tier applications and infrastructure in a group.

Change sets in AWS CloudFormation allow you to preview how your proposed changes to a stack will affect the existing resources and configurations. Instead of applying changes directly to a stack, users create change sets which include a summary of changes, resource replacements, and possible downtimes. Change sets enhance the predictability and control for updates, helping users prevent accidental resource modifications, resource deletion or the creation of unnecessary or unintended resources during updates. Change sets can be created, viewed, and executed from the AWS Management Console or CLI.

Stack policies in AWS CloudFormation prevent unplanned resource updates or deletions. They define what changes are allowed and which resources are protected during stack modifications. A stack policy is a JSON-formatted text file that specifies the allowed or denied actions on defined resources or the entire stack. By implementing stack policies, you can reduce the risk of unintended modifications to critical resources during maintenance or updates, ensuring stability during the cloud infrastructure lifecycle.

Intrinsic functions are built-in functions provided by AWS CloudFormation to assign values or perform calculations on template parameters, resource properties or metadata. They enable dynamic configuration as well as allowing these values to be evaluated and resolved at runtime. Common intrinsic functions include Fn::Join for combining strings, Fn::GetAtt for getting attributes from resources, and Fn::ImportValue for referencing exported outputs from another stack. By utilizing intrinsic functions, you can achieve greater template flexibility and maintainability, ensuring infrastructure updates and modifications are managed efficiently and predictably.

AWS CloudFormation Designer (Designer) is a graphical tool for creating, viewing, and modifying AWS CloudFormation templates. With Designer, you can diagram your template resources using a drag-and-drop interface. As you create, update, and arrange your resources, Designer automatically generates the appropriate changes to your CloudFormation template, typically represented in YAML or JSON formats. This helps you visualize your architecture and validate your templates, ensuring they are logically designed and functioning as expected. Designer can also quickly import existing templates and edit them, providing a convenient way to modify and manage your infrastructure as code without having to manually edit the underlying template.

StackSets extends the functionality of stacks by enabling you to create, update, or delete stacks across multiple accounts and regions with a single CloudFormation template. This is particularly useful for deploying standardized infrastructure environments, managing resources consistently across your organization, and expediting disaster recovery scenarios. StackSets takes care of safely provisioning, updating, or deleting stacks in the specified accounts and regions, with options to conduct these operations sequentially or concurrently. You can also define failure tolerance and maximum concurrency for your StackSet operations, providing fine-grained control over how changes propagate across your accounts and regions.

Drift Detection is a feature in AWS CloudFormation that allows you to detect if the actual stack resources have drifted from the expected stack configuration, as defined by the stack template and applied parameters. Drift is any unintentional change in the stack resources made outside of CloudFormation that leads to discrepancies between the actual and expected stack configuration. By using the drift detection feature, you can identify resources that have drifted, view what has changed, and take necessary actions to remediate the drift, such as updating the template or resources. This helps maintain consistency, compliance, and version control of your infrastructure, ensuring it adheres to the intended configuration.

Custom Resources are user-defined resources in AWS CloudFormation that are created using Amazon S3, AWS Lambda, or other custom endpoints. They serve to extend the functionality of CloudFormation by allowing you to manage custom resources using AWS CloudFormation that are not natively provided by AWS, such as third-party tools or in-house software. Custom resources follow the same management principles as other AWS resources, including creation, update, and deletion through stack operations. With custom resources, you can achieve greater flexibility and control over your templates while keeping your infrastructure and application components in a single, unified configuration.

Rollbacks and Rollback Triggers in AWS CloudFormation enable you to automatically revert your stack to the previous state if a stack operation fails, ensuring stability and minimizing risk during updates. Rollbacks can be configured to occur based on any predefined conditions, such as resource creation failures, update failures, or customer-defined alarms. With Rollback Triggers, you can specify AWS CloudWatch Alarms that, when triggered, automatically initiate a rollback of the stack operation. This allows you to closely monitor your stack resources and automatically revert changes in case of threshold breaches or unexpected issues. These features help you maintain a reliable, consistent state of your infrastructure, minimizing downtime and errors during the evolution of your architectures.