Tarski's schema T asserts that:
(T) x is true if and only if p
where x is the name of any sentence of the language in question and p is the expression which forms the translation of this sentence into the metalanguage.
A typical example is:
'snow is white is true' is true iff snow is white.
Apart from the distinction between object language and metalanguage which avoids paradoxes like the Liar, isn't this (partial) definition of truth in schema T trivial in itself?
(By trivial, I mean that the schema itself, as a sentence of the metalanguage, is an obvious theorem of the metalanguage.)