A glass fermentation vessel, usually in sized in gallon increments for brewing wine in particular (amongst other alcoholic beverages, like hard cider, and whatnot!)

All carboys should be kept clean, and sterilized before putting any fermentable substance in them. The contaminants of just some tiny wild yeast strains or other little critters can turn your wine into vinegar.

Sterilization of carboys can be done using commercial brewing sterilizing chemicals, bleach and water (make sure you rinse well!!), or boiling water. Boiling water for sterilizing is the safest as far as the brewers I know concur. But damn, that stuff is hot, so I have been known to use bleach and water, let the mix sit for a few hours, scrub with a carboy cleaner, and rinse 3-4 times very well with water.

Any amount of bleach will ruin a ferment.

Bleach kills yeast, even the good alcohol making kinds.