The cubic capacity refers to the volume of a cylinder between the upper point inside the cylinder head to the bottom dead centre of the piston. The engine capacity is the sum of all the capacities of all the cylinders taken together, depending on the number of cylinders.
The capacity specified in the car registration document refers to the engine capacity and is measured in cubic centimetres.
In many cases, the engine capacity in litres is added to the model name so you can see it more clearly. For example, the "SEAT Leon 1.6".