The Central Processing Unit or the Processor is the brain of the computer - though considered with zilch intelligence as it is only able to follow instructions.
Every order we give to the computer is sent to the CPU in the computer language (1s and 0s), is then analyzed and finally a reply is sent back in whatever language we have chosen - English, German,...
RAM & Hard Disk Drive:
Random Access Memory is the temporary memory of the computer. RAM is like scrap paper that holds your work while you are working on it or editing it. But as soon as the power is cut, nothing will be saved. For example, RAM is holding up my article while you are reading it right now ; if you haven't saved it and the computer is turned off no trace of it will be found when you turn your computer on again.
That's where the Hard Disk Drive comes to save the day. The Hard Disk Drive is the storage pot of the computer. Whenever you click on the save button, your work will be sent to the HDD. It will be stored there for you to reuse whenever you want.
Now, whenever you want to open a file, the CPU will go searching for it in the HDD and then send it to RAM - the temporary memory - to hold it up while you manipulate it.
This is board inside the case which contains many devices which are all joined with each other. This board is the Central Nervous System of the computer which the CPU and most of the cards (see titles bellow) plug into.
This is a chip - not eatable - which transfers the digital information into the chosen format and displays everything onto the monitor.
The sound card is responsible for putting out the audio files through the speaker or headphones.