Meaning – The term header, refers to the information placed in front of other data known as the body or payload. The header describes the payload and its information to help devices know how the data should be handled.
The term header also refers to the portion of a message that contains control information for the message such as one or more destination fields, name of the originating station, input sequence number, character string indicating the type of message, and priority level for the message.
A header or heading is text at the top of a page in an electronic document or hard copy.
Example of usage – “In Microsoft Word, a header could be created in a document to display the page number of each page. By contrast, a footer is at the bottom of a page in an electronic document or hard copy.”