What are the major parts of a computer and its functions?
Hard drive: Stores information in bytes, a storage unit.
Processor: Processes information from the computer *speed depends on clock speed* and if there is too much information for the processor to handle, it will lag (stutter) and heat up.
Motherboard: Sends electrical signals to each part of the computer in a circuit like pattern.
Fan: This is a very essential part to the computer, as it keeps the parts cool and stops overheating. If there was not a fan built into the processor, in a matter of seconds, it would go up to about 373°K, or 100 degrees C° 212°F. The circuit board in the processor would then melt.
Graphics Card: The visuals that you see when you play video games or use simulations, also lets you see what is on the computer when you are browsing the internet. The graphics card has a mini fan built in but should be supplied with sufficient air flow via other fans. The processor has a mini graphics card in it *if it is of a high quality* but should not be alone if one would be using the computer for gaming.
Hope that helped!
(Note) If you are worried about processor heat, you should download a safe temperature watcher.