Final answer:
The term that describes the response letting both message sender and receiver know that the message was received correctly is called an acknowledgment.
Step-by-step explanation:
The response to a sender's message that allows both the sender and receiver to know that a message was received correctly is called an acknowledgment. This term refers to a signal passed between communicating processes, computers, or devices to signify that a message has been received and understood. In computer networking and telecommunications, an acknowledgment is typically used to ensure reliability in the data transmission process. For instance, when you send an email, the server may send back an acknowledgment to your email client indicating that the message was received. Similarly, in networking protocols like TCP (Transmission Control Protocol), an ACK packet is sent back to the sender to confirm successful receipt of data packets.