what makes fats saturated or unsaturated anyway?

Triglycerides are one molecule of glycerol connected to three fatty acid chains. Fatty acid chains are strings of Carbons with Hydrogens going off either side. Usually there are 4 to 24 of these Carbons. 18 Carbons is the most common. *Fatty acid chains also have an acid group and a methyl group on either end. So a saturated fat is one that is saturated with Hydrogens. That's it! I was surprised a term that's thrown around so much simply meant that. So because it's 'saturated' all of the areas that Carbons could attach to have a hydrogen attached. Because of this it's a straight line.

Saturated fats, because they're straight, take up less space and pack in. This is why foods that contain them - say, the fat around your steak or butter, are solid.

Unsaturated fats are "unsaturated" with hydrogens. In order for everything to be stable and  bonded correctly that means that a couple of bonds in the chain are paired up. These double bond makes a 'kink' in the tail. The kinks take up more space, which is why your olive oil, which is filled with unsaturated goodness, is liquid. The more unsaturated it is, the more liquid it is. Some vegetable oils are solid because they are more saturated, such as cocoa butter and coconut oil.