Apache Airflow is an open-source workflow management platform that was created at Airbnb in 2014 to author, schedule, and monitor complex workflows. It allows users to define workflows as directed acyclic graphs (DAGs) of tasks. The Airflow scheduler then executes the tasks on workers based on dependencies. Airflow is commonly used for ETL pipelines, data processing, machine learning workflows, and automating devops tasks like monitoring cron jobs. Companies like Robinhood and Google use Airflow for complex data workflows and as a managed service on Google Cloud.