The PBA is a development file which you can edit. PVA is a compiled runtime file which is downloaded to the HMI.

Panelbuider 32 can convert the PVA application into a PBA application to allow editing of the file. This is a nice feature, if you don't have access to the original PBA file.

Also, if you upload the file from the PanelView, you will get a PVA file. This file is editable, but I would recommend saving it as a PBA file during development...