Overclocking is when you make a computer part run faster or slower than it did when you
first received it. You'll see CPUs run at "3.0" Ghz for example. Well depending on the CPU and
your cooling options, you might be able to overclock (OC) this CPU to 3.2 Ghz instead. Then it'll
run faster. It might not always mean more FPS (Frames Per Second) in games, but it can both be
fun to do and of course make your computer feel faster. It does create more heat though, thus you need
more and better cooling. Water-cooling is usually the most effective coolant. Most expensive too.
On the Intel side, the CPUs with a K at the end of their name, such as an i5-3570K are "meant" or "able"
to be OC'd; better than those without a K. In other words, the K ones have been "unlocked" by Intel.
The other CPU manufacturer, AMD, also use the K to denote that something can be OC'd. Other times they
call something a "Black Edition" which is just like Intels "K" edition. If your budget isn't too great, it's not
recommended that you try to OC; because you need more parts and that adds cost. OC'ing can of course
break your hardware; though this rarely happens if you're careful. There's lots of guides online on how to
overclock. There's many popular programs too, such as MSIs Afterburner. People will typically OC their CPUs
and then some might OC their GPUs too. Some motherboards come with "1-click" OC features as well; such
as the Asus Maximus I think. One way that OC'ing adds cost, is if you for instance got a CPU like the i5-3570K,
that's good at OC'ing. Well in order to keep it cool, you'll have to buy an "aftermarket" CPU-fan. While if you
didn't want to OC, you wouldn't have to buy the fan, because you'd get a "stock" one automatically when you
buy the various computer parts. K-series (and Black edition) CPUs are also generally more expensive too, as
the manufacturers (Intel and AMD) think it's a powerful/nice feature to be able to OC. Not everyone wants
to OC however and so sometimes "UnderClock" instead. This is done for various reasons, besides just
for fun. If you UnderClock the CPU in your smartphone for instance, then you'll be able to extend the battery
life, as the CPU now runs slower and doesn't consume as much power. In a desktop you might do it to
reduce how much heat your CPU generates. This should be all you need to know about OC'ing, before
actually diving in yourself.
As for motherboards you'll probably want to look for ones listed "ATX" as they're "Standard" or "Normal"
sized ones. This has some upgrade value to it, moreso than motherboard which are smaller. Such as
micro-ATX or mini. PlanarX999 came up with some pretty alright builds; do note that the motherboard
in the first one isn't an ATX one.