Do you speak binary? Can you comprehend machine code? If I gave you a sheet full of 1s and 0s could you tell me what it means/does? Your operating system functions as that translator in your PC. It converts those 1s and 0s, yes/no, on/off values into a readable language that you will understand.
If curious, check out this long post I wrote on the 10 most important concepts about Operating System. You'll understand how your computer works in a much more detailed way.