TDEE is 2/3rds (or more) comprised of BMR.
TDEE is Total Daily Energy Expenditure. BMR is Basal Metabolic Rate. TDEE is BMR + caloric cost of typical daily activity level.
BMR is usually about 2/3rds or more of TDEE, which means that we burn a bunch of calories just sustaining life. Even very active people typically don’t get their TDEE more than 1.5x their BMR.