What the function transmitDatablock and activateGhosting does.

I am a TSE Owner, i can't understand what does the transmitDatablock and activateGhosting function done in the Load a mission part, how it is usefull.

Also explain me how does the following script works and where is %this.inv[%data.getName()]; is declared.

function ShapeBase::getInventory(%this,%data)
{
// Return the current inventory amount
return %this.inv[%data.getName()];
}