Rego 101: Introduction to Rego` is an introductory blog post series that covers the basics of Rego, a declarative query language used in the Open Policy Agent (OPA) framework. The series aims to provide a gentle introduction to writing Rego policy as code and its applications. Rego is used to write policies that apply programming practices such as version control and modular design to evaluate cloud and infrastructure as code resources. OPA evaluates these policies and delivers decisions on compliance, adding speed and flexibility to the development lifecycle. The series covers key concepts including rules, queries, assignment, input, and evaluation with examples and interactive tools like the Rego Playground. It also discusses applications in Snyk IaC+ and security design for developers.