Carbohydrates

Carbohydrates, which are primarily contained in plants, are the main source of energy for the human body.

Types of carbs:

Monosaccharides - the simplest type of sugars, absorbed within the digestion process, which include: glucose found in almost all types of fruits, fructose, contained in each sweet fruit, and last but not least galactose, contained in milk; simple sugars are easily absorbed by the organism
Dissacharides are more complex as their name stems from the two sugar chains that they are made up of. In order for them to be fully absorbed, they have to break down to monosacharides. Dissacharides are the refined sugar, saccharose (contained in watermelons, beetroot and other sweet fruits), lactose (aka sugar of milk) as well as maltose (malt sugar).

polysaccharides are the winners in terms of complexity. They come in the greatest molecular weight due to the fact that they are made up of thousands of monosaccharides molecules. They also have to break down to monosaccharides so as to be completely absorbed. Polysaccharides are the starchy foods, such as cereals, nuts, legumes, root crops, etc. Starchy foods are harder to digest so when combined inappropriately, they slow down the digesting to a great extent. Other foods rich in starch are also seeds, pasta, legumes and many others.

Simple sugars

Heavily sugar-packed foods:

Plant sugars (honey and overripe fruits);
Milk sugars (milk);
Artificial sugars (white refined sugar, which is extremely unhealthy for the human body and so its consumption has to be avoided)

Fruit sugars are the fastest to digest.

The so-called lactose aka milk sugar is contained in the milk as its proportion is about 5 %.

According to specialists in this sphere, their consumption has to be cut down on since they reflect quite badly on the normal functions of the digestive system
Some starchy foods are pretty much hard to digest when combined with other nutrients, unlike many other varieties of starch.
I advise you to combine starchy foods with many veggies, excluding tomatoes
Children have better exclude such foods from their menues
Improve the consumption of seeds, cereals, fruits, veggies (including the juices themselves) as well as legumes

Carbohydrates are the main source of energy for the human body;
Carbohydrates are divided into monosaccharides and polysaccharides
Simple sugars are: plant, milk and artificial sugars (avoid the last type)
Complex sugars slow down the digestive system as they are also hard to combine with other types of foods.