Steps have always been serial in GitHub Actions — if you wanted parallelism, you split into multiple jobs, paid the runner startup overhead, and wired up artifact passing or service dependencies by hand. The new `background: true` flag changes that: mark a step async and the runner immediately moves to the next one. `wait` and `wait-all` let you gate later steps on specific background steps or all of them at once. The practical unlock is real. Spin up a test database while simultaneously building the app. Run lint and type-check side by side without splitting into separate jobs. For pipelines where job-level parallelism felt like overkill, this fills a gap that's been there since day one.