Your BMR is the number of calories your body burns at complete rest, just to keep you alive. It's the base layer of your daily calorie needs.
Basal Metabolic Rate is the energy your body uses at rest for breathing, circulation and keeping your organs running. It's typically 60–70% of the calories you burn in a day.
BMR is your at-rest burn. TDEE adds all your daily activity on top. You never want to eat below your BMR for long — for fat loss, build your deficit from your TDEE instead.
BMR is calories burned at rest; TDEE is BMR plus all your daily movement and exercise. Use TDEE, not BMR, to set your eating calories.
No. Eating below your BMR for extended periods can harm your metabolism, hormones and muscle. Create your deficit from your TDEE instead.