This measurement is the total volume of all the engine's cylinders, also known as the engine displacement. This is one of many aspects of an engine that determine its horsepower, but generally speaking a greater size indicates more power.
Fuel economy is a measurement of fuel efficiency, based on how far you can travel with a certain amount of petrol (gasoline). A lower fuel economy means the car will be cheaper to run.
A turbocharger compresses the air entering the cylinders, allowing more air (and therefore more fuel) to be added - resulting in a more powerful explosion. This leads to an increase in horsepower without increasing the size and weight of the engine.
An intake valve allows the air/fuel mixture to enter the combustion chamber. An engine with more valves tends to increase performance.
Torque is a measurement of an engine’s power, closely related to horsepower. More torque indicates a more powerful vehicle and is also a good indication of its acceleration.
Horsepower is the most common unit for measuring the power of an engine.