Moutai (or Maotai) is distilled from fermented sorghum. It's similar to soju (Korean) and shoju (Japanese). The most famous Moutai is Kweichow Moutai. I have a dozen or so bottles at home. Moutai originated, I believe, in the 17th century.
I only drink it when I am in China (a very common ceremonial drink; and I usually over-consume!) or when Chinese friends are visiting. Interestingly, I have never had a hangover when drinking it, although I do drink a lot of water.
As for the moutai at Costco, I have not seen it before.