hello abhishek,..

in simple words, metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function. There are three general categories of body types (somatotypes): ectomorph, mesomorph, and endomorph. Very few people fall perfectly into one of the three categories. People are often a mix of characteristics. Additionally, years of training and good nutrition can change the outward appearance of one's body.  Your resting metabolic rate (RMR) is the number of calories your body burns to maintain vital body functions such as heart rate, brain function and breathing.

hope this information was useful to you,..

all the best for your bright future..