Motherboard (Send & Receive information throughout the computer) 
Power Supply (Provides Power to the Computer)
Soundcard (Processes audio and helps provide a output through a external device or integrated speakers) 
GPU (Generate Graphics which can then be displayed through a external device like a monitor)
Monitor (Output Information)
Cooling Fans (Regulate Computer Temperatures/ensure hardware doesn't overheat) 
SSD/HDD (permanent Data storage)
CPU (Processes all information and communicates with your pc to allow functions to be executed)
Bluetooth/Internet/Ethernet (Allow external connections to your pc) 
I/O Board (Input/Output information to external devices)^
Printer (Input or Output Information from or to the pc, Ex. Print, Scan)
Keyboard (Input Information)
Mouse (Input Information)