That’s always a weird way to phrase it since the Aztec Empire was established relatively recently…lots of universities are older than that. The universities in Bologna and Paris are even older than Oxford. 1249 (or actually 1248) was when Oxford was recognized by a royal charter, but there is evidence (as in the previous thread that you linked to) that something was happening there as early as 1096.

I will point to u/Erft’s previous answer, which discusses how modern universities developed the Bachelor/Master/Doctor system, but their answer starts out with a good discussion of medieval universities. Essentially you would study the “liberal arts”. These were divided into the “Trivium” (grammar, logic, rhetoric) and the “Quadrivium” (arithmetic, geometry, music, astronomy). After mastering those you could also continue studying law and/or theology (and later, in a few universities, medicine - but not at Oxford).

You wouldn’t study practical skills like blacksmithing. For that you wouldn’t need a formal education at a university.

Check out Erft’s answer for a longer discussion and some sources about medieval universities.