Hey @orion,
I just answered a question about comparing Flowable with Apache Airflow and Prefect Flowable vs Airflow and Prefect - #2 by filiphr. I think that it is similar to your question.
Flowable has various number of use cases. It can be used for defining and orchestrating business processes through events. However, it can also be used to start processes and workflows manually or automatically through timers as well.
Cheers,
Filip