Declare which task depends on which and let the scheduler decide what can run now, what must wait, and what to retry.
A kitchen pass: the sauce can't go out before it's made, two cooks work in parallel on independent dishes, and if one burns you redo that dish, not the service.
A pipeline that can only run 'now' can never be repaired — and every pipeline eventually needs repairing.
An orchestrator turns a pile of scripts into a dependency graph. Tasks are nodes, dependencies are edges, and because the graph is acyclic there is always a valid order. The scheduler then handles everything cron can't: it runs independent branches in parallel, holds a task until its inputs exist, retries transient failures with backoff, and — crucially — keeps one run per logical interval, so a failed day can be re-run on its own without disturbing the others. That last property is what makes the DAG worth the operational weight: a pipeline that can only run 'now' can never be repaired.
An orchestrator like Airflow, Dagster or Prefect models the pipeline as a directed acyclic graph of tasks. It runs independent branches in parallel, blocks a task until its upstream succeeds, retries with backoff, and keeps one isolated run per scheduled interval so any single day can be re-run. Cron gives you none of that — it gives you a time and a hope.
What is Apache Airflow? — codebasics, 8:41