Can you please explain compression - what is means, and how it works - why higher compression means more speed......thanks

The simple answer is the compression refers to how much the air fuel mixture is squeezed in the combustion chamber. The more it is compressed the greater the force on the piston when the air fuel mixture burns and expands. The greater force means more power.

Dont try the old trick of High Compression, (like 11.5 or 12 to 1) no pump gas to support that these days.