Another way of phrasing it:
Suppose I have an E-T-L flow.
And one day I decide I want to have another L be triggered from the data produced by the T.
Maybe one day I have five Ls that need to be triggered from the data produced by the T.
I don't want to start adding more *L*s to the same flow because that would get messy after awhile.
Also, maybe I want a flow that just does the T-L and not the E, because I already have the data output from E from a previous flow and E takes awhile and I don't want to do it again.