Fats are found in foods such as meat, fish, seeds, nuts and dairy products. All oils derived from plant sources are also fats.
They are mainly stored form of energy & therefore, have more energy value. When consumed in excess they promote building stores of energy in the form of fat, in the body.
For this reason, although some fat is vital, too much fat in the diet leads to weight gain. Eggs, milk, meat, oils, curd, cheese, cashewnut, coconut, etc. are the major food sources of fat.