When a flowchart is needed that does not require any user interaction (e.g. a calculation, some background process that needs to run, etc.), you use an action flowchart. If your action flowchart contains sub-flowcharts there can not be any user interaction in one of the sub-flowcharts. In some situations, for example exposing webservice functionality, you can ONLY use action flowcharts. Action flowcharts can be distinguised from regular flowcharts by the lightning bolt in the icon.