What are trans fatty acids and are they good / bad type of fat?

Common & very toxic: Most trans fats come from partially hydrogenated oils found in many processed & fried foods like french fries & donuts. Simply put, trans fats are highly toxic.They cause inflammation, raise cholesterol & may cause up to 100, 000 deaths in the us from heart disease each year. They also increase risk of alzheimer's disease, diabetes, obesity, depression & infertility. See my comment for some links.