I guess I would explain it as an agreed upon way of talking to each other, say you decide you want to text, or call, or send a card. A protocol is like that. It’s not the data just the transmission method. A protocol controls the data stream, the hand shaking (when it is OK to start sending data, which port, where to send it). A data packet sent using a protocol is like a letter, with a sender, intended receiver, stamp (signature, key, CRC, etc.).
I guess I would explain it as an agreed upon way of talking to each other, say you decide you want to text, or call, or send a card. A protocol is like that. It’s not the data just the transmission method. A protocol controls the data stream, the hand shaking (when it is OK to start sending data, which port, where to send it). A data packet sent using a protocol is like a letter, with a sender, intended receiver, stamp (signature, key, CRC, etc.).