What is the 1.5L or 2.0L indicates in car?

basically it relates to the volume of the piston's compression1.5Leater motor compresses the space in the cylinder witch is 1.5 liters of air and gas and in a 2.0leater motor the space is 2.0 liters so you can see that you can get more gas and air mix in a 2.0 liters motor for a more powerful car unless turbo is on the 1.5 because a turbo kind of forces more air in to the cylinder so you can get more gas and get more power