Tautology is when something is repeated in a sentence but using different words. It can be used to enrich the sentence but also it can be needless repetition.
5 statements that would produce a tautology:
1. Lets order a toast sandwich.
2. In my opinion, I think he is right.
3. The Gobi is a very dry desert.
4. The hurricane hit in 3 p.m. in the afternoon.
5. Don't worry, everything is well and good.