I am still working through the Next.js conf videos in tandem with my v16 upgrade. I am on Auroa's awesome talk about composition and would like to use her ui Boundary tool. I feel like this question is fundamental to my understanding of the whole shift.. in this component, what is the purpose/difference between hydration and rendering? Sorry, I've pulled the code and watched the video several times.
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https://github.com/aurorascharff/next16-commerce/blob/a81079800d507c83a13785f690f77a7038a4aa72/components/internal/Boundary.tsx