The AEIOU keyboard model is a simpler replacement for the QWERTY/QWERTZ or DVORAK keyboard models. It contains less keys that were only included in computers because they were mainly used a work tool, is smaller than other keyboard models, has every key take an equal amount of space and has the main latin (english) alphabet vowels (A, E, I, O, U, Y) together on the top left.
The CTRL key was renamed into ALT1 and the ALT key into ALT2 for the sake of less confusion. SHIFT was renamed into BIG. ENTER has been shortened to ENT. The "windows" key was changed into a SYST (system) key. The top right key is for turning the machine off/on. The top two empty spaces are set for custom keys or diacritics based on what language the keyboard is trying to support.
The keys that contain more than one symbol use the top symbol by default and you can get them to use the bottom one by holding BIG.