What does the word 'acknowledge' mean?

Question

Question ATPL - Airline Transport Pilot license - IFR Communications

QuizVDS · Accepted Answer

Let me know that you have received and understood this message

QuizVDS · Answer

Pass me the following information

QuizVDS · Answer

Repeat all of this message back to me exactly as received

QuizVDS · Answer

Repeat all of your last transmission

Id 74 - ATPL - What does the word 'acknowledge' mean?