If a phrase which contradicts itself is an oxymoron - eg 'non-stop flight', then is there a name given to a phrase which repeats its meaning, such as 'true fact'?
You could also call it a redundancy. A tautology is a statement which predicates an identical thing, suggesting a cause e.g. 'Chlorine whitens clothes because of its bleaching effect.' The fault is that 'whitens' and 'bleaching' mean (in this case) the same thing. So the statement does not give the reason why chlorine has that effect, it simply restates the effect using different words. (The word 'because' suggests the statement is an explanation.)