1 - Basal metabolic rate
The basal metabolic rate is the amount of energy expended daily at rest. This is the minimum energy needed for the body to function, without any additional physical activity.
2 - Physical activities
The physical activity level (PAL) is a factor used to to express the additional physical activity and is used to calculate the total energy required per day.
3 - Total daily calories
The base caloric intake is the amount of calories your metabolism needs based on your level of physical activity.
The total calories are the actual total calories per day. This might include e.g. a surplus or deficit if you are bulking or cutting. Alternatively you might just enter yourself the amount of calories if you know the value.