Why do they mesaure engenes in cubic centimeters?

Answer 1

This is one of the factors that determines the peak horsepower and peak torque which the engine will be capable of delivering. Here's why. When one of the engine's pistons is at the bottom of its stroke, so that its cyclinder has maximum capacity, that cyclinder will have a volume equal to the rating of the engine in cubic centimetres divided by the number of engine cylinders. The cylinder volume is how much air and fuel mixture available for burning in one cycle of that cylinder. The bigger the cylinder volume the greater the volume of air-fuel mixture available and, therefore, the greater the energy that can be released during that cycle, all other things being equal.

Of course, engines vary in many other ways, so total cylinder volume is just one aspect of their performance. There's also compression ratio, number and placement of valves per cylinder, cylinder head shape, piston shape, valve timing, and so on and so on. Volume is just something that most people find it easy to understand.