The payload is the part of transmitted data that is the actual intended message or packet.
The payload excludes any headers (ie metadata) used for delivery or processing purpose.
The term is borrowed from transportation, where payload refers to the part of the load that pays for transportation.
The most common usage of the term is in the context of packet and message protocols, to differentiate the protocol overhead from the actual data.
For example, a JSON web service response might be:
{
"data":{
"message":"Hello, world!"
}
}
where: