sugar; white sugar
Few pantries don't contain a bag, bin, or box of granulated sugar. Whether made from sugar beets or sugar cane, white sugar is 99.9% pure sucrose that's refined and processed into small crystals.
Aside from making things taste sweet, sugar performs many other essential functions in baking; it keeps baked goods soft and moist, creates tenderness, and helps in leavening, and can create that crunchy, sweet crust often found on brownies, pound cakes, muffins, and cookies. It also deepens color and flavor, which is why it's often added to bread dough. That last trait is useful in savory cooking, too, where a little sugar added to, say onions, will help caramelize them.
Compared to other white sugars (superfine and confectioners' sugar), granulated sugar has the largest crystals.
8 oz. = 1 cup
Other natural sweeteners, such as honey and agave, can substitute with some tweaking to the recipe and a likely change in flavor and texture.
While shopping for sugar, keep in mind that the sugar industry has not standardized its labels, so stay alert to inconsistencies between brands and stick with what gives you the best results. Though taste is practically identical, some bakers claim that cane sugar gives better results than beet sugar (which is less expensive) in baking. C&H brand is made from cane sugar, but not all brands list what their sugar is made from, and the source can vary.
Kept in a cool dry place, white sugar lasts forever.