It is a little more complex than that. Simple sugars are broken into 3 main categories: Galactose, Fructose, and Glucose. The 3 are called Monosacharides and each represent a simple molecule of just a few atoms. Granulated sugar for example is basically a mix of glucose and fructose. Most fruits contain Sucrose, a mix of glucose and fructose as well.

Then there are Polysaccharides which are simply long chains of monosaccharides, like starches and carbohydrates. Grains, potatoes, and legumes contain these long chains.

FYI this is the simple version relevant to the nutritional discussion, as a chemist will tell you there are actually 4 different types - monosaccharides, disaccharides, oligosaccharides, and polysaccharides.

Sugar is a compact form of energy for our body. It is not outright bad, as we need it to live, but definitely can be abused and contribute to a variety of health problems when it is.

Sugars exist in just about everything we eat that was derived from something that was once living. Plants contain sugar for the same reason we need them, as a form of energy.

What is important is that the simple molecules are easy for the body to break down and consume. So they are fast. Longer molecules take more time and represent a form of energy storage. There are other factors, like the need for enzymes and ability to dissolve in water, but that is for a deeper discussion.

Our body chemistry uses these different types of sugar in various ways, based upon their molecular bonds. So don't get too caught up in the various names. Yes, juices contain sugar but are not entirely sugar.

Reading labels. Looking at the Ingredient labels only gives you part of the story. If the first ingredient is High Fructose Corn Syrup, you can bet the food contains a high percentage of simple sugars. But also go to the Nutritional label to see the quantity. Those two will help you understand the type and amount of sugar in the item.

Hope this helps.