Although Sous Vide technically means "under vacuum," most folks now use it as a blanket term for all low-temperature cooking that's done with a water circulator. Essentially this type of cookery encapsulates your food in plastic (vacuum or ziplock packing) and then gently brings the internal temperature up by bathing in a warm water bath, which is precisely maintained by the water circulator. Moisture loss is next to nothing as everything is contained in the bag and overcooking is impossible as the food never goes over the temp of the bath. There are some pork belly sous-vide recipes that call for four days of cooking!
With the price of water circulators down below the $200 range, I've made a video explaining almost everything one needs to know to fully understand the science of low temp/sous-vide cooking, and how you can mimic the texture of filet mignon with the much cheaper cut of sirloin filet. I also added information about the Searz-all and an induction cooktop to round out a segment that takes a glimpse into the future of the American Kitchen.