When something has 44g of carbs, 6g of that is fiber, 12g sugar, and 26 starch, what is the starch? I mean, is that good or bad or neither?
Starch is (IIRC) the "carrier" for the polysaccharides (glucose, etc.). When you divide it out by sugars and fibers and etc., the "starch" part of the equation is the ... I guess you'd say the leftover after you pull the sugars trients out. It actually doesn't make a whole lot of sense to divide it that way, IMO. Starch and sugars are digested and processed by the body. Fiber is non-digestible and helps "clean" your digestive system.
I don't tend to think of starch as "good" or "bad" necessarily - for me I pay more attention to the sugar content and the balance of nutrients to calories. I like some bang for my caloric buck, so to speak.
What is the deal with sodium? Is that the salt content? And why is it bad? Water retention?
Sodium is salt, yes, as well as other permutations of salt type minerals. It's one of those things that you can't eliminate, but we get far too much of these days.
The RDA for sodium is 2400mg per day. Some people can use a little more, some can use a little less. Most people get 3x or 4x that from eating fast food, processed food, etc. In fact there's more sodium in most frozen dinners than there is in a shake from the salt shaker. Isn't that scary?
Sodium will cause you to retain water. Basically, the simple way it works is that your blood needs a balance of electrolytes (sodium and other minerals) and fluid in order to run properly. When you consume more sodium (and other minerals), then your body holds on to water to maintain that balance. When you consume less sodium, your body can release water so that the electrolytes aren't too diluted.
Eating too much on a regular basis can mess up your electrolyte balance which affects all parts of your body. Not just your blood pressure, heart, etc., but it can damage your kidneys and liver as well - as they're primarily responsible for filtering your blood and eliminating wastes and excess.
Hope that helps w/out being too simplistic.