and some geeky ones just for fun:
PSU - Power Supply Unit - The device that pulls in 110/220 and outputs 12, 5, and 3.5V to various pieces inside the computer
CPU - central processing unit - the traffic cop, mathmatician, and translator rolled into one. Everything goes through here to get somewhere else on the computer
mobo - motherboard - the giant circuit board that everything plugs into. If this goes bad its usually too expensive to fix
RAM - random access memory - These are "sticks" that have copper connectors down one side and stick out from the motherboard. They are used as your current working space and are cleared when you turn off the computer. Also called "memory"
HD - hard drive - long term storage. programs are pulled out of storage on the HD and placed into RAM before you can start using them. this is what takes so long to launch programs because hard drives are "slow" compared to the rest of the computer
HSF, HS, HS/F - Heatsink and fan combination - heatsinks pull waste heat energy from chips like the CPU. Most will come with a fan already attached for extra cooling.