Let's look at several HTTP requests to learn the basic structure of these messages, and how the various elements communicate important information from the client/browser to the API service. 
Follow the instructions at HTTPie to download the CLI tool and follow along.

 

Install: Link

 

RUN:

Get all the Request header / body and Response header and body:

http get https://api.github.com/users/zhentian-wan

 

Get only request printed:

http get --print=HB https://api.github.com/users/zhentian-wan

See the options: Link