The phrase "copy that" is often used in military, aviation, and law enforcement communications, where it is essential that messages are received and understood accurately. It can also be used in other contexts, such as customer service or technical support, where it is important to ensure that the recipient has understood the information that has been provided.
When someone says "copy that," they are essentially saying "I understand the message that you have sent." It is a way of confirming that the message has been received and understood, and that there is no need to repeat it.
The term "copy that" is often used in conjunction with other radio communication terms, such as "over" and "out." "Over" is used to indicate that the speaker has finished speaking and that it is the other person's turn to talk. "Out" is used to indicate that the speaker is finished speaking and that they are signing off.
So, when someone says "copy that, over," they are essentially saying "I understand the message that you have sent, and now it is your turn to speak."