Lipids are also known in common terms as fats. There are four basic types of fats: Monounsaturated and polyunsaturated are the good kinds, and saturated and trans fats are the bad kinds. Good fats are actually good for you and have many beneficial affects, while bad fats are bad (kinda obvious, I know). Foods like nuts, avocados, olives, salmon, and green vegetables (not white) all have large amounts of good fats. Bad fats are present in almost all candies, chips, crackers, and other high carb junk food in high amounts.
One note on Strange's answer: Not all polyunsaturated fats are equally "good". Current research has tended to suggest that an equal 1:1 balance between omega-3 polyunsaturated fatty acids and omega-6 ones are important to heart health and weight management.
Corn oil is especially high in omega-6 relative to it's omega-3 content (almost none). In addition, corn oil has a high saturated fat content. And since most of our meat is corn-fed, our is higher in omega-6 than omega-3 at around 4:1 to 6:1 for conventional beef (from an article I read and cannot find right now). Beef fed a natural grass diet (whose grasses are very high in omega-3) contain a balance of fatty acids around 2-3:1 omega-6 to omega-3.
Instead of corn oil, canola oil offers more omega-3 fatty acids, 2:1 o6 vs o3, and other foods like Salmon and Mackerel, flax oil (1:3 o6:o3), and some green leafy vegetables.
Lard, butter, shortening, deep-fried ice-cream, fatty meats, high-fat dairy, (whipping cream, half and half. They don't actually have lipids themselves, but these saturated fatty foods can turn into excess fat in your blood that contributes to heart disease, several cancers, type 2 diabetes, and strokes.
