Terraform is an infrastructure-as-code tool that simplifies the management of cloud resources. It allows users to define their infrastructure in a declarative language and automates the deployment and management across multiple cloud providers. Terraform's use cases include single-cloud and multi-cloud deployments, managing Kubernetes clusters, implementing high availability and disaster recovery configurations, building consistent environments, and integrating with other tools for better workflows. It can also be used with infrastructure management platforms like Spacelift to enhance its capabilities further.