I like analogies.
Hard drives are like a big cupboard. It's where all your shit gets stored. Same for computers. Install stuff and save stuff and it goes to the hard drive. Bigger hard drive = more space for crap.
Memory (Or RAM) is like a desk. You know when you try to figure shit out and you end up writing a bajillion things on notes that get scattered around your desk? Same thing with RAM. It's right there so it's quick to grab, but there isn't much space on the desk and whenever you're finished (Or, more importantly, you think you are!) shit ends up getting chucked in the bin. Or saved. To the cupboard/hard drive!
CPUs (And cores) are like you. You figure that shit out yourself. That's what a CPU does. Think of more CPUs = more people to help. Cores are the heart of CPUs. If a CPU has one core it's like only you working. Two cores means there's two of you! And so on, so you work better and faster! But, like if there really was two of you then both of you wouldn't necessarily draw on the same picture! Likewise, just because there's more than one core doesn't mean it'll actually be doing stuff (But it should).
A motherboard is like the room everything is in. By itself, it's just a room. But better ones may have nooks and crannies for neat things! Everything sits in the room and is thus connected. That's a motherboard.
Finally, a GPU (Or, video card) is like a dedicated artist. You (The CPU!) write down what you want drawn. You then give it to the artist who draws it much quicker (But not better!) than you could.
Beep, beep. That's a computer!
"Worst case scenario I'll get arrested for public nudity.
Best case scenerio I'll get arrested for public nudity with a boner. It's win win." ~ Dave
"Also Yoshi is the most important person in all of Australia." ~ Zepherin