The main parts of an AIO liquid cooler are -

• Cold plate/water block: Metal plate (usually copper) sits on the CPU with thermal paste for good contact. Inside are microfins or channels.
• Pump: Circulates coolant through the block, tubes, and radiator (often integrated into the block in AIO coolers).
• Tubes: Carry coolant between block and radiator.
• Radiator: Dense fin array that transfers heat to air.
• Fans: Push/pull air through the radiator.
• Coolant: Typically water with glycol and corrosion/biological inhibitors.

The heat path follows the below process - 

• CPU generates heat.
• Heat conducts through the IHS and thermal paste into the cold plate.
• Coolant flowing through microchannels absorbs the heat (convection).
• Pump moves the hot coolant to the radiator.
• Radiator fins spread heat; fans move air to remove it.
• Cooled coolant returns to the block and the cycle repeats.

In our opinion, if you’re doing a lot of intensive gaming or have a heavy workload on your CPU, having an upgraded cooling system is definitely worth it.