Basal metabolic rate (BMR), also called the resting metabolic rate, It is the amount of energy needed to support the body's most basic functions when at rest in a neutral, or non-stressful, environment. The BMR is the number of calories a specific human need per day to stay alive.
A calorie is a unit of energy. In nutrition and everyday language, calories refer to energy consumption through eating and drinking, and energy usage through physical activity. For example, an apple may have 80 calories, while a 1 mile walk might use up about 100 calories.
In the modern world our consumption of calories is higher than what we use. So we must do some physical workout to burn the extra calories to maintain a healthy weight.