Terraform is an infrastructure as code tool created by HashiCorp in 2014, which lets you describe an infrastructure (servers, networks, databases, accounts, DNS) in text files, then create and modify it automatically with one or more cloud providers.
You write the desired state in a declarative language, HCL. The plan command computes the gap with what exists and shows what will change; apply applies the changes. Terraform keeps track of what it manages in a state file, which has to be stored and protected carefully. Hundreds of providers cover AWS, Azure, Google Cloud, OVHcloud, Scaleway, but also services such as Cloudflare or Datadog.
In 2023, HashiCorp moved Terraform to a non open source license. Part of the community then created OpenTofu, an open source fork hosted by the Linux Foundation and compatible with existing configurations. HashiCorp has since been acquired by IBM.
Why it matters when hiring
Terraform is a core skill for a DevOps, Platform Engineer or Cloud Engineer. Surface-level experience shows quickly: the candidate has edited existing files without ever designing the module structure or managing shared state. Ask how they handle environments, secrets and a corrupted state. Whether they work on Terraform or OpenTofu is also a good starting point.