Every car engine has quite a few details, ranging from cylinder count to compression ratios. How does changing the compression ratio affect the engine?

What makes a diesel engine different to a regular gas engine, and is one better than the other?

Water Oil Cooled 4 Cylinder 4 Stroke Inline Engine, Four Valves Per Cylinder ...

SI, 4 Stroke, 4 Valve, Single Cylinder, Liquid Cooled, Reverse Inclined ...