There's a little clock inside a Computer chip Processor. When you "overclock" it you're basically using software to turn the clock around and around. So through some unexplained part of physics, time turns quicker within the processor. So it's part theory of relativity, and part computer genius. Because you're making the clock inside spin faster, time outside slows down. At least to the computer chip, so its moving faster when viewed by us. The extra heat output is an unexplained phenomena that no one still can explain to this day.
That website is good.