BMR or RMR stands for "basal or resting metabolic rate" and is the number of calories that you need to eat each day just to exist (without factoring in physical activity or the energy cost of breaking down food).
Often, after getting your BMR tested, the people at the testing facility will provide an estimate of how many total calories your body burns each day based on your BMR and the amount of activity you do. This is called your TDEE (total daily energy expenditure).
It’s important to understand that your estimated TDEE is exactly that—an estimate. If you’re eating your estimated TDEE and are not losing weight, the estimate is too high. This is due to your metabolism being slower than what would be expected based on your BMR, body weight, and activity level.
Depending on how slow your metabolism is, it may be a good idea to reverse diet and work on building your metabolism before trying to lose any more weight. This will set you up for success in the future and get your calories closer to what your projected TDEE should be.