You are more than entitled not to know what the word 'performative' means. It is a new word and an ugly word, and perhaps it doesnot mean anything very much. But at any rate there is one thing in its favor, it is not a profound word.

Sentences are not as such either true or false.

The beginning of sense, not to say wisdom, is to realize that 'doing an action,' as used in philosophy, is a highly abstract expression--it is a stand-in used in the place of any (or almost any?) verb with a personal subject, in the same sort of way that 'thing' is a stand-in for anynoun substantive, and 'quality' a stand-in for the adjective.

The theory of truth is a series of truisms.

Fact is richer than diction.

Usually it is uses of words, not words in themselves, that are properly called vague.

Is it true or false that Belfast is north of London? That the galaxy is the shape of a fried egg? That Beethoven was a drunkard? That Wellington won the battle of Waterloo? There are various degrees and dimensions of success in making statements: the statements fit the facts always more or less loosely, in different ways on different occasions for different intents and purposes.