Can someone explain engine size to me?

It all has to do with how the equidistant length of the flux capacitor and the regurging complex HT rods. If they are closer together then, well it could be a disaster...Trust me, I know about these things.

It is how many cubic inches or centimeters are in the cylinders. The bigger the number, the more gas that is burned in the cylinders and as a result more power produced.

It isn't related to the fuel capacity of the gas tank.

As each piston moves through its cycle in the cylinder the volume of space it moves through is it’s displacement. If a 3.3 liter engine has 6 cylinders, each one displaces .55liters

On average, the greater the total displacement, the more power the engine is capable of generating but other factors also play a part.

3.3 is the size of the engine. It has nothing to do with how much gas it holds.

Basically size & power. The bigger the number, the more capable it is usually. It's not about gas

If your car is a 3.3L then I'm guessing it's a V6?

the tanks takes 19 gallons but the engine size is in litres thats all

The internal volume of all cylinders added together.

FYI to viewers I edited the question to sound more simple. Soz 😁