How many calories should I eat to lose weight?

I'm currently 62kg but started at 65 and I'm trying to get to 56 or 57. I'm 167 tall and a teenager. I've been eating about 1200 calories for almost three weeks but I'm not sure if this is a healthy amount although I have been losing weight. Ive heard of a BMR and TDEE and using an online calculator worked out my BMR is 1490 and TDEE is 1788 but don't really get what they mean.