What is tautological?

Could you please clarify what you mean by "tautological"? It seems to be a term that refers to a statement or phrase that is redundant or repetitive in nature, essentially saying the same thing twice in different words. For example, the phrase "free gift" is tautological because "gift" inherently implies that it is free. Is that the correct understanding of the term, or am I missing something? Could you provide an example of a tautological statement to further illustrate the concept?