What is Shaoxing Wine, and why's it in almost every Chinese recipe?

"Liaojiu, a.k.a. Shaoxing wine." I know I say that quite a bit in these recipes, so here, I wanted to explain myself a bit. We'll go over the varieties of Shaoxing wine (plus, the Shaoxing wine-like objects labeled such in English), a bit about the historical background, and why/how it's used when cooking.

Now note that neither of us are brewers or anything, so our knowledge of how to make this rice wine's rather... elementary. We'd be happy to answer any questions, but we probably won't make rice wine on this channel anytime soon. Maybe one day though?