QWERTY... to anyone who types, this is the most common keyboard layout available today. And even though almost everyone has used this layout at some point in their lives, most people don't realize how this bizarre layout came to be.
The most common misconception is that QWERTY was created out of efficiency. To make typing easier. Quite the contrary. Back in the mechanical typewriter days, Christopher Latham Sholes invented the first commercial typewriter. The very first keyboard was actually laid out as ABCDEFG. But back then, as people would type faster, the hammers (those things that punch the letters onto the paper) would hit each other and get jammed more and more frequently.
In an effort to keep his machines from jamming, Sholes decided to move the most frequently used letters away from each other to prevent them from jamming when typing at high speed. This consequently gave rise to the other misconception that QWERTY was invented to slow down typists and to keep from having to re-engineer the typewriter mechanism. Well, it actually did both at the time. But basically, it was just to prevent mechanical jamming of the type arms.
Despite the odd layout, and inefficient placements of the letters, most modern typists can hit speeds of 70wpm, while others can reach as high as 120wpm.
The more modern keyboard layout, the Dvorak keyboard, has been created with efficiency, speed, and carpal tunnel syndrome in mind. Controversially claiming typing speeds of 400wpm once a typist gets familiar with the keys.