Open Policy Agent (OPA) is an open-source, general policy engine that enables organizations to define policies as code and enforce them across various systems, including microservices, API gateways, CI/CD pipelines, and Kubernetes. OPA's policy language, Rego, allows developers to write scalable and declarative rules for different types of services. Rego is a high-level language that works with JSON data, making it suitable for use in various systems. By using OPA and Rego, organizations can improve the security and governance of their software systems, reduce the risk of policy changes, and make it easier to maintain and scan policies for vulnerabilities.