The target audience is those who do. It's a complex enough topic that it's reasonable the author chose not to explain it (an early question of "where do I begin

The target audience is those who do. It's a complex enough topic that it's reasonable the author chose not to explain it (an early question of "where do I begin?" doesn't have an easy answer). "Denormalization" is saving data in the "wrong" place in a database so you don't have to do a join to a different table. It's "normalized" if the textual data[0] (e.g. a name) is all in the "correct" place (e.g. the user profile) and not in the "wrong" place (e.g. the user's comment). In a normalized database, the comment displaying the username would have a reference to the user record, which has a reference to the user profile record (assuming those are separate; they're often not). https://en.wikipedia.org/wiki/Third_normal_form https://en.wikipedia.org/wiki/Third_normal_form [0] "Non-primary-key data" but I don't know how helpful the extra technical jargon is.