State tax filing

California uses form FTB 3514 to determine whether you qualify to claim the Earned Income Tax Credit, YCTC, and FYTC, provide information about your qualifying children, if applicable, and to figure the amount of your credits.

If you may qualify for Earned Income Credit, and you have any income on your Federal return on  Schedule 1, Line 3, this may be what the program is asking about. Do you have either a Schedule C or Schedule F in your return? See screenshot below from Form 3514:

From the instructions: Line e – Business code

Use the six-digit code from federal Schedule C (Form 1040) or Schedule F (Form 1040), box B.

If you do have a Schedule C or Schedule F, go back to the business section of TurboTax and enter the appropriate sic-digit code.

As @MayaD noted earlier, If the form doesn't apply to you, try to delete it by following these steps:

1. Select the Tax Tools option on your left menu bar

2. Select Tools

3. Select the Delete a form option under Other Helpful links 

4. Look for Form 3514 in the list and delete it

If you have a Schedule C in your return and you don't have a business, you can delete it following the same method.