What's a calorie anyway?

When you hear the word, it conjures up images of eating cakes, candies and other food. Calories should be viewed as energy that keeps you going. The only problem is that you get too many of them, you end up stockpilling unused energy and that's what turn into fat.
What exactly is a calorie? It's a mesure of energy: the capacity to do work. Science defines calorie as the amount of energy required to raise the temperature of 1 gram of water by 1 degree celsius.
The simple functional purpose of calorie: to fuel our body's day to day activities.
How many calories should I eat to lose weight