Basal Metabolic Rate is the minimum number of calories your body needs daily. If you stayed in bed all day, your body would still burn this many calories. The more active you are, the more calories your body needs, so you should ALWAYS be eating more than this number in calories each day.
Your BMR will dictate how easily it is to put weight on or off. Think of it as a fire and the food you eat are the logs on the fire. The bigger the fire gets the easier it can burn the logs! You can increase your Basal Metabolic Rate through a combination of exercise, recovery and nutrition.