All-in-One computers are computers that are built into the monitor. These used to be popular, but with the rise of everyone having their own notebook PC, this may not make as much sense especially since the AiO has to a little more expensive by using cutting edge design to be as thin as possible. There is even at least 1 AiO that can not fit a 3.5mm audio jack in the computer except through the side. AiOs likely do not have any drives, nor are they upgradable or repairable. When purchasing the AiO, you should go as best as you can, and make it last as long as possible.