How does it work?

The first thing to understand, – it’s REALLY EASY

I use an analogy of posting a letter

You write the senders and receivers address on the envelope with the message inside

The post is delivered as per the address

Once received the envelope is opened and message received

HTTP requests (in fact all communication) works the same way

The message is wrapped in an ‘envelope’ with addresses

On receiving, the addresses are removed and message is delivered

More on that process and HTTP messages construction here: