First, one blog is not going to cover it.
Second, two blogs just not going to work either.
Let's start with the basics, counting calories. A calorie is nothing more than a unit of energy we get from food. 100 calories from an apple is the same as 100 calories from refined sugar which is the same as 100 calories from red meat.
Now there are two things to consider when selecting foods or drinks for our caloric intake.

So now you are thinking, "Well, I'll just down a couple spoonfuls of white sugar and have all the energy I need." Um...WRONG!!!
Number Two: is about digestibility of food. Our bodies have evolved over at least a billionty years. It takes more than just calories to fuel us. The quality of food is as important as the quantity. You would actually gain more energy from a spoonful of Turbinado sugar than refined white sugar. The less commercially processed the food is, the more we can gain from it.
The body digests, filters and distributes nutrients to where they are needed. If you drink a soda pop, you may get some energy from it. The body may send some of the moisture to parts of the body needing it. And then it looks at the crap that is left over and promptly sends it to the tush (we may need this later) storage area.

Guess what? There are some things your body will not digest and if you are lucky, it will pass through. Otherwise, it stores these "things" in the tush, thighs, belly or where-ever you store your potential energy.
One final note. Just remember we do not eat to lose weight, we eat to live. You eat well, you live well. If you want to know the quality of your fuel, just take notes of everything you eat in one week. And be honest to yourself. You deserve at least that.