Creating commission splits
There are two reasons you may want to utilize the Commission Splits feature.
1) When you create a Sales Opportunity the opportunity is assigned to you. There may be times when you want to create an opportunity on a record that is not assigned to you and you want the opportunity to be assigned to the person who is assigned to the contact.
2) There may also be times where you have multiple people on your team working on a given opportunity. If you wish to track the commissions for these opportunities and split them between multiple team members then you can use the "commission splits" feature in the "Sales module".
How to Create a Commission Split (Admin Tab)