kCal is the short term for kilocalories. A kilocalorie is 1000 calories. It is a measure of energy (typically used to express the energy content in food). The term joules or kilojoules is also used in some circumstances.
There are different definitions of metabolism. Basal metabolic rate is defined as the minimum energy required to keep a person in a steady state (homeostasis). This means the energy required to keep the person alive without them gaining or losing weight.(water excluded). The amount of energy required depends on factors such as gender, body weight and composition etc. For example, a person with a high muscle mass percentage and low body fat percentage, would require more energy than a person of the same weight, but with a high body fat percentage or lower muscle mass percentage.