The Additional Forms tab in the Applicant Summary shows any information recorded against your User Defined Forms that have been set up with the Location set to Applicant > Summmary Additional Forms.
Setting up User Defined Forms is covered in the User Defined Forms in PICSWeb Configuration section of the help.
You can navigate between the different forms using the tabs at the top of this section. In each tab, you can select the Edit icon to open a window where you can edit answers for the current form.
Once you have made any changes, select Save to confirm them or Cancel to discard them.