The Printing Press was the most revolutionary piece of equipment ever created. The printing press allowed the creation and duplication of many different documents, so that they could be spread around the world.
Reading and Writing were skills only obtained by the rich and religious leaders. The creation of the printing press made it easier for the general public to have access to reading materials, and slowly, overtime, they learned how to read.
Enough of that boring history. Let's learn why we refer to capital letters as 'uppercase' and regular leaders, as 'lower case'. The original printing press had two different cases on it.
Each case was identical, except for the fact that one of the cases had only capital letters (A, B, C...) While the other case had regular letters (a, b, c...)
People started referring to capital letters as Upper Case letters because they were literally on the upper case of the printing press!