A stock pot is deep pot, much taller than it is wide, made of metal with straight sides.
It will have short handles on each side, and a lid, which is sometimes glass.
The sizes are usually quite generous, to allow something like a turkey carcass to be easily stuffed in. A minimum size would be 8 quarts (7 1/2 litres), but the sky’s the limit for upper size, all the way up to 100 quarts (94 litres) once you include restaurant supply stores in your shopping scope.
The design helps slow evaporation of the water the food items are being simmered in. The goal is to make a flavourful stock, not a concentrated one.
The height causes a “convection current” to develop in the stock, helping to keep heat slowly flowing in the pot through the ingredients.
Stocks shouldn’t boil, just simmer. You want to slowly leach all the flavours out of the ingredients.
Dutch oven; any other large pot.