Bun is an all-in-one toolkit for running, building, testing, and debugging JavaScript and TypeScript applications, offering speed comparable to Node.js and Deno, making it suitable for edge computing. Environment variables in Bun can be accessed using traditional Node.js methods or the new Bun way, allowing developers to store configurations and secrets securely. Bun supports native .env files, which eliminates the need for additional packages, while also providing an option to use a secret manager like Infisical to manage complex environments and security requirements. Using Infisical offers benefits such as end-to-end encrypted secrets, version-controlled environment variables, automatic prevention of hardcoded secrets, and seamless integration with various tools and infrastructure.