There is a line of various trucks with advertising on the side parked by the side of the road, with the 'Grilled Cheese Truck 'and the 'Calbi' truck in focus.
there are many food trucks
If the trucks are selling grilled cheese and calbi then they must be food trucks.
Line of means many and Grilled Cheese Truck and Calbi truck means food trucks.
If there is a line of trucks there are many trucks.