VAPP is more or less what you would get with Boeing if you add the additionals for wind and gusts. In addition to this the Airbus own Groundspeed Mini function influences VAPP.
VLS is calles "lowest selectable speed". Sounds like this is the lowest speed you could select by turning the speed knob on the FCU (Boeing calls the FCU MCP). But that's not the case. The VLS is the slowest speed the Airbus lets you fly. The automatics in the normal life prevent flying below this speed, but you still can dial in a lower speed than that on the FCU.
This statedment may not be exact, as I am now flying a Boeing af several years on Airbus. So please don't shoot me.