I'm new

It's a NEAT calculation (if you're talking about MFP)

Which means based on your age, height, gender, current weight and stated activity level (eg without purposeful exercise) and weight goal loss a week, MFP has calculates your BRM plus an allowance for your activity

so if you said sedentary, which most do because most of us have desk jobs then you would get your BMR x 1.2 = MFP guideline .. this will be no lower than 1200 for a woman

MFP is telling you if you just do no exercise this is how much you should eat to lose what you want to

When you exercise you burn more calories and you should eat them back too .. it's a great motivator and you need to fuel your body appropriately to exercise and preservse as much LBM as you lose weight
- be aware that most take 50%-75% of MFP database burns as it overestimates

(also at the end of the day the one who eats the most and loses, wins)