Carb is short for carbohydrate, one of the main types of nutrients your body uses for energy. When you eat bread, pasta, rice, potatoes, or fruit, you're eating carbs. Your body breaks down carbohydrates into glucose, a simple sugar that fuels your muscles, brain, and everything else that keeps you going.

Athletes often eat carb-heavy meals before big games or races because carbohydrates provide quick, reliable energy. Marathon runners might load up on pasta the night before a race. On the other hand, someone trying to lose weight might eat fewer carbs and more protein, since extra carbohydrates can be stored as fat.

You'll hear people talk about “good carbs” and “bad carbs.” Good carbs like whole grains, fruits, and vegetables contain fiber and digest slowly, giving you steady energy. Bad carbs like candy and soda digest quickly and can cause energy spikes and crashes. A bowl of oatmeal with berries will fuel your morning much better than a donut, even though both are high in carbs.

The word is casual and conversational. In scientific writing, you'd use the full word carbohydrate, but in everyday conversation, most people just say carb.