What is unhydrogenated margarine?

Answer 1

It's margarine, which hasn't been hydrogenated.

Hence, unhydrogenated margarine.

I can improve on that, because I don't think that answer helped much.

hydrogenation is the process they use to make liquid vegetable oil turn firm and spreadable. Animal fats, like butter and lard, are firm when kept cool, but vegetable fats are less saturated so with a few exceptions (such as coconut oil) they are liquid even when cool. You can't spread liquid oil, so the hydrogenation process was created to change the texture by artificially saturating the oil and making it more firm. In recent years it's become more and more apparent that this process is very bad for human health, because the type of saturated fat that is created by this process is very bad for heart health. For many years people thought butter was bad for the heart and margarine was good, but we now know that's really not true.

To address this, manufacturers are trying to make margarine that's not so bad for you: there are lightly hydrogentated options available. They are much softer than regular magarine (you can squirt them out of a squeeze bottle) but a bit thicker than regular oil. Typically, the harder the margarine, the more hydrogenated it is. So the stuff that comes in squares is usually much worse than the softer stuff in tubs, and the liquidy stuff is another step better.

There are some natural brands of margarine (earth balance is one) that do not hydrogenate. They use blends of oils including firmer vegetable fats like palm oil, so they can make a healthier maragarine. There is a lot of debate as to what kind of butter/margarine is best for people and the planet (harvesting palm oil is a major environmental issue) so read up!