By Felicia, on July 11th, 2011
There are four types of Fat: saturated, monounsaturated, polyunsaturated and the dreaded trans fat. I am going to give a simple definition of all of these.
Saturated Fat: A fat that remains primarily solid at room temperature; examples are butter, lard and coconut oil.
Monounsaturated Fat and Polyunsaturated Fat: There is a chemical definition out there about molecules and double bonds that define these fats and below are the sources where I got my definitions but ultimately these fats are liquid at room temperature; olive oil, peanut oil, soy oil.
Trans Fat: Trans fat is a manmade fat made from the process of hydrogenation which makes unsaturated fat act like saturated fat. An example of this is the ingredient partially hydrogenated oil.
Following the rule of eating whole foods, saturated fats are naturally found in nature as are some unsaturated fats, e.g. olive oil. But, be aware that the unsaturated oils such as vegetable oils are not a natural thing found in vegetables, they require a lot of processing. When looking at fats, think whether they come from a natural place or an unnatural process.
Sources: http://fitnessblackbook.com/diet-tips/the-four-types-of-fat-sorting-out-the-confusion-of-dietary-fats/ and http://www.medterms.com.