Sentence:  Gödel's model is an example of a simple type of inner model that might be called a "definable transitive inner model"3), where the universe is replaced by a transitive subuniverse defined within <WSD>ZF</WSD>, the membership relation is just the original one restricted to the subuniverse, and where the axioms of <WSD>ZF</WSD> relativized to the subuniverse, are provable within <WSD>ZF</WSD>. 
Meaning of the word marked with <WSD> tags:  Zermelo-Fraenkel set theory, without the axiom of choice.