What do we call needless repetition that does not add meaning or understanding?

The term that describes needless repetition that does not add meaning or understanding is tautology. Tautology occurs when a statement reiterates a concept using different words without advancing the idea. For example, saying "free gift" is tautological because a gift is, by definition, free, and thus adds no new information. This can lead to redundancy in writing or speech, which can detract from clarity and engagement.

Reiteration, while similar, generally implies repeating something for emphasis and can enhance understanding. Rhetoric refers to the art of persuasive speaking or writing and is not limited to repetition. Hyperbole is a figure of speech that involves exaggerated statements or claims not meant to be taken literally; it serves a different purpose altogether. Therefore, tautology is the precise term for the type of repetition mentioned in the question.