You’ve written, or are writing, your book.
You want to share it with the world.
This opens up a whole new line of questions about publishing.
One question I am asked regularly, “Why do I need my own barcode?”
Simply; you need your own barcode if you intend to print your own books for direct sale to alternative channels, other than Amazon, or if you want to distribute through independent bookshops.
Amazon will supply a barcode free of charge when you publish your book and it saves you the expense (and space) of creating stock, but you will make less money per book.
However if you can only foresee needing about 50 copies for your nearest and dearest, I’d recommend ordering them through Amazon at your authors rate. Or order on-line, which will earn some royalties back on each copy. Useful for cash flow and keeping your box room from becoming a room of boxes!
Finally; why use Amazon to publish your book? Because it’s the biggest platform and ‘go to’ place for books.