How does Shopify affiliate program work

Recently, I have read of members success with Shopify which has made me curious about what Shopify is.

So I have been online, asked the usual questions in Google about what Shopify is but I can't understand it. In all my years of researching affiliate programs, this one has left me puzzled.

I can clearly see that Shopify has an affiliate program. It appears that one can apply to be an affiliate without paying to join Shopify.

But, what is it that an affiliate of Shopify is promoting?

I understand that Shopify is an e-commerce program. My understanding stops there!

However, I am interested in whether the success affiliates are having is from being a paid member of Shopify and promoting their own products (if that's what Shopify is about)

or -

Are these affiliates having success by promoting the Shopify e-commerce program?

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