Dev, test, QA, prod — before you type a single command anywhere, know which world you're standing in. This is the shortest lesson in the track and the one that prevents the worst mistakes in it.
Done
Same commands. Different worlds.
Nothing you learn in the rest of this track changes between environments — the terminal, the queries, the API calls are identical. The only thing that changes is what they land on. That's why this lesson came first: every lab ahead of you runs in a sandbox where breaking things is the point, and the discipline of always knowing which world you're in is what will eventually earn you — or your agents — the keys to the ones that matter.