Chef and Pulumi allow you to use a general-purpose programming language (GPL) to manage infrastructure as code: Chef supports Ruby; Pulumi supports a wide variety of GPLs, including JavaScript, TypeScript, Python, Go, C#, Java, and others. Terraform, Puppet, Ansible, CloudFormation, and OpenStack Heat each use a domain-specific language (DSL) to manage infrastructure as code: Terraform uses HCL; Puppet uses Puppet Language; Ansible, CloudFormation, and OpenStack Heat use YAML (CloudFormation also supports JSON).

The distinction between GPLs and DSLs is not entirely clear-cut — it’s more of a helpful mental model than a clean, separate categorization — but the basic idea is that DSLs are designed for use in one specific domain, whereas GPLs can be used across a broad range of domains. For example, the HCL code you write for Terraform works only with Terraform and is limited solely to the functionality supported by Terraform, such as deploying infrastructure. This is in contrast to using a GPL such as JavaScript with Pulumi, where the code you write can not only manage infrastructure using Pulumi libraries but also perform almost any other programming task you wish, such as run a web app (in fact, Pulumi offers an Automation API you can use to embed Pulumi within your application code), perform complicated control logic (loops, conditionals, and abstraction are all easier to do in a GPL than a DSL), run various validations and tests, integrate with other tools and APIs, and so on.