I have heard that, one should cut down their trans fat consumption. But I am confused what are these trans fat and what foods have them?

Trans fats are unsaturated fats that have been processed. Eating trans fats increases the levels of ‘bad’ cholesterol and decreases the levels of ‘good’ cholesterol in the body which is a major risk factor for heart disease. It is important to lower the amounts of trans fats you eat to help you stay healthy. Trans fats are found in many packaged foods and also in butter and some margarines.