protocol is the set of rules of behaviour,usually in the form of a code that describes the expected behaviour
humans need a language to talk with each other,language contains grammer..etc,likewise computer components are communicate with each other by using protocol.
ex:web server and browser can coomunicate by same languge here the langugae they used is http.

what is protocol

protocol is nothing but set of rules between communicating entities
in order to communicate they must follow this rules and behave accordingly
ex:http
we send http request to a server ,their is aggreement between server and browser to what to do if server gets request
it understands the request by seeing data,and responds accordingly,then browser task to understand response and display correct data to user

in case of http the rules are found in rfc documents ,based on those rules only code is implemented for protocol,like what will happen if we use get instead of GET in request all rules are in the form of rfc documents.

incase of http we send just an http request which is called message ,protocol is not just only message it tells how and when messages are send(incase of tcp) when tcp protocl send syn packet
,wait for ack
,it is the rules specified for tcp.
finally any system will send and recieve data there must be a protocol used .