Chef and Ansible encourage a procedural style where you write code that specifies, step-by-step, how to to achieve some desired end state. Terraform, CloudFormation, Pulumi, Heat, and Puppet all encourage a more declarative style where you write code that specifies your desired end state, and the IAC tool itself is responsible for figuring out how to achieve that state.

To demonstrate the difference, let’s go through an example. Imagine that you want to deploy 10 servers (EC2 Instances in AWS lingo) to run an AMI with ID ami-0fb653ca2d3203ac1 (Ubuntu 20.04). Here is a simplified example of an Ansible template that does this using a procedural approach: