Amazon Affiliate Built In payment method

Hi,

I'll launch my ecommerce with amazon affiliate program soonly,
I see sometimes website with built-in payment method directly on the website I already searched on google and BHW but no way to find informations about this technique...
I have knowledge in development (PHP, JS ect...) and I would like to know if someone know how to do this ? Or a hint from where to start...

Thank you by advance!

Ps: Is it correct to say "soonly" in english ?