What are the differences between sugar and fruit sugar? Or refined and unrefined sugar? What does it even mean?

Fructose (fruit sugar), sucrose (Refined, or table sugar), lactose (Sugar in dairy products), glucose (A simple sugar that the body produces for energy; it's also manufactured from many plant starches); they're all sugars, from different sources. Your body doesn't care, and processes all types of sugar the same way.

sugar is NOT bad for anyone! Some is necessary in our food plans.
All plant derived foods contain some amount of "sugar" called carbohydrate in them. This is converted in digestion to glucose for use in the muscles and other parts of the body for fuel. ALL sugars are converted to glucose no matter which source they come from. There is no bad and no good in any of them unless the person eating them is diabetic then we have to count each and every gram and use moderation in eating or drinking them.

All hookum. You body turns sugars into glucose, so it doesn't matter. People come up with the stupidest BS.

Fruit sugar sounds better.