Basal metabolic rate, this sentence consists of three words, if we break this sentence into three separate words and explain the meaning of these three words separately.
Basal means basic or lowest.
Metabolic or Metabolism is a physiological process through which the body produces energy from food stored in the body.
And here rate means quantity or amount.
The body requires minimal amount of energy to perform various internal functions.
This energy comes from metabolism.
Even if we are not doing any work, the body needs a certain amount of energy to carry out various internal functions such as breathing, blood circulation, heart function, brain function etc.
This specific amount of energy is not the same for all people.
Here, this required minimum energy for a certain body is called besal Metabolic Rate or BMR of That body.