Application level protocol like Http and FTP

Question

Ok , so a group of people or scientists or company i don't know who but someone defined some rules that in order to send messages or receive or to download or send files or anything like that in a big network that is in the network of network which is called as internet at application level (browser or server level) we have to follow some rules,

so protocols like Http and FTP has been defined ,

Today a junior asked me what actually a protocol is ? I said set of rules like if you say hmm and then i say umm then again you say hmm and i say umm then it is a protocol, like that Http is an application level protocol preceeded by network level protocol.

then he asked where is it defined in the brwoser , where are the drivers of http? and i really got stuck , like i am a useless software engineer.

 

Where is it defined? omg i really don't know.