What's the difference on filling single or divorced

None really.  It's only available as two separate choices because divorced people sometimes don't think of themselves as single when they have not been divorced very long.  You can choose either.

There's really no such thing as filing divorced, it's just a choice for marital status in the program, not filing status.

If you pick Divorced it will still put Single on your tax return.

Divorced parents can sometimes also qualify for head of Household filing status and, the program will ask questions to determine if you qualify, so Divorced can also lead to a Head of Household filing status.

@Anita01  thank you! this answer clarifies this question.