The term V-8 when applied to engines refers to the fact that the engine has eight cylinders that are arranged in the form of a "V" when looked at from the front. So, cylinder 1 slopes up at an angle to the left, cylinder 2 at an angle to the right, and so forth.
One of the advantages of such an arrangement is that the engine runs a lot smoother than engines with all the cylinders arranged in line.

The sound produced by a V-8 engine is unmistakable.

Engines with more or fewer cylinders arranged in a V are found too. In Formula 1 racing, for example, nearly all cars have V-10 engines.