Header: An information structure that precedes and identifies the information that follows, such as a block of bytes in communication.
Trailer: An information typically occupying several bytes, at the tail end of a block of transmitted data and often containing a checksum or other error-checking data useful for confirming the accuracy and status of the transmission.
Addition and Removal of Headers and Trailers:
Headers and Trailers concept is related to the OSI model. In data communication from one device to another the “Sender” appends header and passes it to the lower layer while ‘Receiver’ removes header and passes it to upper layer. Headers are added at layer 6,5,4,3 & 2 while Trailer is added at layer 2