Fully hydrogenated vegetable oil shortenings contain no trans-fats like partially hydrogenated shortenings. Hydrogenation is a process used to make oils thicker by forcing hydrogen atoms into the polyunsaturated fatty acid molecules that make up oil. Partial hydrogenation makes oil semi-solid (like margarine), while full hydrogenation turns the oil into a solid (more like beef fat).
They're not used very often in cooking because they're solid at room temperature, which makes them difficult to use.
Fully hydrogenated oils can be used for cooking when they're blended with non-hydrogenated polyunsaturated oils to make them softer. Crisco brand shortening contains a mixture of fully hydrogenated oils and regular soybean oil.
Harvard School of Public Health. "Shining the Spotlight On Trans-Fats." http://www.hsph.harvard.edu/nutritionsource/nutrition-news/transfats/.