Carbohydrate is not the evil substance you thought it is. It is an essential part of your diet, and plays a vital role in your health. It is found in nearly all foods, though in highly variable amounts. Foods such as bread, pasta, rice, potatoes, legumes and fruit have a high percentage of carbohydrates.

Energy Source

Carbohydrate (commonly called 'carbs') is one of the main energy sources in food, and is the body's preferred source of energy. During digestion, carbohydrates are broken down into glucose, which is then absorbed into the bloodstream, from which it an be delivered to the cells of the body and used for energy.
Glucose, the product of carbohydrate digestion, is an essential fuel for the brain. The brain cells, unlike other cells of the body, cannot use any alternate fuel and must therefore have a constant supply of glucose.

Does it make you fat?

Carbohydrate is just another energy source like fats and protein. Carbohydrates themselves do not make you fat, it is eating too much of any of the these energy sources compared to the amount of activity that you do that will make you store the excess energy sources and make you gain weight.