CICS: Difference between transaction and task

Transaction and Task are interchangeably used.  We programmers/users call it as a "transaction", where as from CICS perspective, CICS calls it as a "task". Task begins when you enter the transaction id in the CICS "blank screen" and ends when the control return back to CICS. A CICS transaction task may execute several programs.

In the below diagram, task begins from the beginning of program 1 and task ends when control is returned to CICS from program 4.

CICS tran id -> Program 1 -> Program 2 -> Program 3 -> Program 4 -> CICS