Full Idea
The truth predicate, says Tarski, should be defined in terms of the more primitive satisfaction relation: the relation of being 'true of'. The fundamental notion is a formula (containing the free variables) being true of a sequence of objects as values.
Gist of Idea
We can define the truth predicate using 'true of' (satisfaction) for variables and some objects
Source
report of Alfred Tarski (The Concept of Truth for Formalized Languages [1933]) by Leon Horsten - The Tarskian Turn 06.3
Book Reference
Horsten,Leon: 'The Tarskian Turn' [MIT 2011], p.74