Application Lifecycle Management (ALM) in Power Platform refers to the end-to-end process of managing the creation, deployment, testing, and maintenance of Power Apps, Power Automate (Flow), and Power BI solutions.
Environment variables are defined at the environment level and can be accessed by any solution that is part of that environment. This means that if you have multiple solutions within the same environment, you can define an environment variable once and use it across all your solutions.