Molasses is a flavorsome liquid sweetener.
Molasses is produced during the manufacture of sugar. Sugarcane juice is boiled down to crystallize out the sugar it contains. The remaining liquid is light molasses. Light molasses may be processed again to produce more sugar and the less-sweet dark molasses, which in turn may be processed yet again to produce blackstrap molasses. Molasses may be sulfured to preserve it; this adds a bad taste though.
When the sugarcane juice is boiled less, with no sugar being removed, the result is cane syrup. Unusually dark cane syrup is often sold as molasses. It can be considered a sort of extra-light molasses, with a milder flavor than true molasses.
Dark treacle is a common substitution for molasses. Since brown sugar is made from sugar with molasses added, brown sugar can be a substitute if plain sugar can be removed from the recipe. One cup of dark brown sugar contains one cup of sugar plus 2 to 8 tablespoons (1/8 to 1/2 cup) of molasses.