Fundamental Question about rebrand and resell

I am sure many people browse on Alibaba as a reseller. However, the product from Alibaba pretty much all the product is designed by someone, and then Alibaba manufacturers produce it.

But reseller can buy the same product, then rebrand and resell on somewhere else? How does it work?

For instance, Herman Miller Eames chair should be a protected product. Couple months ago I saw a lot chair on Amazon looks similar to Eames. Let’s say I am seller didn’t realize this Herman Miller existed. And purchase similar chair from Alibaba, also rebar and it to “cossychair”. Then, when customer ask, is this Herman Miller Eames chair. How do we answer? Why does reselling exist?