In logic, a tautology is something that is true in all circumstances.
In conversation, tautology either comes down to stating the obvious The cat is either gray or it is not gray or to repeating the same thing twice in a different way: I went to see him personally.
Try to think of your examples of tautology or find some famous examples from songs, poetry, fiction, etc.
To be, or not to be, that is the question (Hamlet, Shakespeare)