What is the difference between calories, "energy", and fat?!

What is the difference between calories, "energy", and fat?

supposedly you gain weight when you consume more calories than you burn. In addition, gaining weight= becoming fat, an apparent indicator that fat is the equivalent of (extra) calories. Calories are also often referred to as energy, i.e. energy that can/needs to be burned, yet even if you have a lot of extra fat (calories) you would still need to eat to survive, i.e. you would not be able to survive off of the extra energy (calories). So what exactly is the difference between calories, energy, and fat? And if calories and energy are the same thing then why do you still have to eat to survive even if you are fat (have extra calories)? Why are you not just able to survive off of the extra stored calories (energy)?

1 week ago
I have heard it said that the reason you are not able to survive without eating is because the extra stored energy (calories) does not have the necessary components(vitamins, e.t.c.) needed to survive, and therefore even if you drew upon your fat energy reserves you would still not be getting the essential nutrients needed for survival So if this is the case then why is it that your body extracts all of the other nutrients that are contained in food and still uses them even if you eat too much, yet it will not "use" (get rid of) the fat?

Calories are a easure of heat, or energy.
Fat contains 9 calories per gram.
Carbs contain 4 calories per gram.
You need energy to move and think and do all of your body functions. If you are taking in more energy than you expend, then the body stores it as fat or glycogen.
If you are not taking in calories, your body will first use stored carbs(glycogen) and then stored fat fot energy. If that is gone it will use protein or energy.
Your body also needs to function, vitamins and minerals and protein to make body tissue. You need to take these in every day. The fat soluble vitamins can be stored in your body, (A<D<E<K) The water soluble like C and B need to be taken in daily. Generally your body only takes in what it needs of these, and can not store them.
You have cells breaking down all the time and sloughing off, so you need to take in protein.
If you are not taking in minerals, your body may take the calcium out of the teeth to maintain the bones or other uses of calcium like clotting and nerve transmission.
High protein diets that force the body to use protein for energy require that you drink alot of water to wash away the excess nitrogen that is part of the protein, but not used for energy.