what is header

Header : exists in both request and response 
	is metadata about the request 
	It's a key value pair 

	few common header type is 
	Accept header to specify what format you want to get your result
		only if the api itself support 
	Content Type 
		in request header : 
		to specify what kind of data we are sending 
			to the server 
		in response header : 
			what was the contenttype we got as response