Bisque is a term used for once fired ceramics ready to paint. Its a hard porous surface ready to be painted. Bisque can be painted with glazes, underglazes(with a clear gloss glaze over it) and fired to be food or water safe.
Or painted with acrylics and spray or brush glazed and is ornamental only. However if you wish to use the item for food or water, only glazes or underglazes can be fired in a kiln to make it food and water safe.
NOTE: Acrylic paints are NOT food and water safe nor firable. Acrylic paints are strictly ornamental. Plastercraft can only be painted with acrylics therefore plastercraft is NOT firable. Bisque can be painted with either way. If you are painting with acrylics, you can have the best of both products, bisque or plastercraft.