What is Flow Execution Policy?

[Econdoc]

Can someone explain (fully please, I am new at this) what the different options of Flow Execution Policy do? What are the "costs" and "benefits" of each choice? I truly do not find the descriptions self-explanatory.
Thanks again.

[Bushmills]

That describes how Automagic will deal with flows which are retriggered while still executing as result of the previous activation. Some flows you may want to complete first, before relaunching, others you don't want to relaunch at all while still running. Some you want run for every received trigger, regardless of whether one or several previous instances are still running. What to choose here is what makes most sense for the flow in question.