Environment variables are key/value pairs that are passed from parent process to child process when the child is first created. A convention has also arisen where these can be put into environment files so the overarching system (for example, docker) can load them from a consistent place (without having to add them to your shell and risk leakage across projects) and then pass them down to child processes in typical environment variable fashion.

Also there are no sections like there are in ini files.