Anachronisms refer to chronological inconsistencies. In the context of typography, it means using a type that doesn't belong to a particular historical period.

An example of anachronism in typography would be using a script reminiscent of Medieval Europe for a text about Ancient Egypt. Typefaces like Carolingian Minuscule and Pfeffer Mediæval evoke associations with the Middle Ages. Considering that the latest Ancient Egyptian dynasty ended at least 200 years before the Middle Ages, neither typeface is a good fit for the topic.

To avoid anachronisms, do your research and learn the history and origins of fonts. This is especially important when deviating from standard sans serif and serif typefaces.