Well It's pretty simple.
You can think of it like a mail truck and ordering a catalog.
You send out the order for the catalog.
You put the order in your mail box, which gets to your mail truck guy.
Then he sends it through the mail to the specific address for the catalog.
The company with the catalog goes ok they want this.
Then sends back the catalog through the mail.
Sending it eventually to your mail guy.
Who then brings it to your house.
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