Terraform is HashiCorp’s infrastructure-as-code tool for declaratively provisioning and managing resources across cloud providers, SaaS, and on-prem systems. Users write configuration in HCL (HashiCorp Configuration Language), Terraform computes the difference between that configuration and a recorded state file, and then calls provider APIs to reconcile the real world with the declared intent.
Its extensibility comes from providers: separate binaries that expose typed resources and data sources for AWS, Azure, Google Cloud, Kubernetes, GitHub, Cloudflare, Datadog, and thousands of other systems published on the Terraform Registry. The core engine builds a dependency graph from resource references, runs plan to produce a reviewable diff, then apply to execute it in the right order. State can live locally or in a remote backend (S3, GCS, Terraform Cloud, HTTP) with locking to prevent concurrent writes; modules package reusable configuration, and workspaces model multiple environments against the same code.
HashiCorp relicensed Terraform from MPL-2.0 to the Business Source License (BUSL-1.1) in 2023, which triggered the OpenTofu fork now governed by the Linux Foundation. Both share the provider ecosystem and HCL language, and Terraform remains the de facto standard for cloud provisioning alongside Pulumi, Crossplane, and AWS CDK.
