You can think of weekly commissions as being your compensation for any "new" business that week. This could include your one-time retail customers or a new advocate enrollment!
Monthly commissions are bonuses and enhanced commission that are accrued from the production of your entire organization. This is where you will be compensated for Preferred Customers and your downline advocates' orders. These commissions are paid at the end of each monthly period.
For more information about commissions and the compensation plan, refer to this video: