What is "Amazon AWS Access Key ID" and "Amazon AWS Secret Access Key"?
To successfully generate Amazon feeds you need your list of targeted keywords and personal Amazon credentials.
Amazon credentials include: Amazon Access Key, Amazon Secret Key, Amazon Associates ID
To obtain all needed Amazon credentials and be able to generate Amazon feeds you need to sign up for the Amazon affiliate program and for Amazon product advertising API.
The Product Advertising API provides programmatic access to Amazon’s product selection and discovery functionality so that you can advertise Amazon products to monetize your website. When you sign up for Product Advertising API you obtain Access Key and Secret Key. They are used to personalize your Amazon product search. You use these keys in the Amazon Feeds generator at RSS Ground.
Amazon also provides you with Access and Secret keys when you sign up for Amazon Web Service. But you still need to sign up for Product Advertising API to be able to search for Amazon products. And if you have your keys both in AWS and in Product Advertising API, you should use those from Product Advertising API.
Please see the user tutorial on how to sign up for Amazon services and obtain Amazon keys.