If you are an independent contractor reporting on Schedule C (Self-Employed), it's asking for your business name. A TurboTax interview question may ask you if your business name is the same as your actual name, or if your business has a different name. For many people the business name is the same as their actual name (in which case Line C is left blank), while others have actually named their business something else and enter it on Line C. Again, the interview should ask the questions to properly fill that part of the Schedule C
If you are using Online Deluxe, be aware Online Deluxe cannot handle Schedule C with expenses. Online Deluxe can only handle Schedule C income without any expenses. If you have any Schedule C expenses, then in Online TurboTax you would need the Self-Employed Edition to report them.
