Deconstruction & Derrida:in brief:-

There is nothing outside of the text.
The deconstruction is the theory or practice of reading which questions & claims to subvert or undermine the assumption that the system of language provides ground that adequate to establish the boundaries,the coherence or unity of the determinant meanings of the literary text.
A new way of reading text.it goes beyond the traditional way of reading texts.
Text has in itself some elements that deconstruct the structure of that text.
It differs from structuralist view that meaning lies within the text.
Deconstructionist says that the work is made of words & words have no definite meaning. It is the reader who creates meanings. Words can't give meaning.
In essay 'Structure,sign & play' Derrida gives terms like:-
Decentering the center:-
Derrida deconstruct the metaphysics of presence.
There is nothing like truth apart from language.
He tries to prove that structurality of the structure does not indicate the presence, it's free play of signs.
Supplementarity:-
A literary text is a work of language & language is in state of ever changing evolutionary.
Language being in the flux is not ever the same.it always gaining in new elements & loosing the older once.
Literary work being made of language,there is no certainty of it's meaning.
Meaning of the work of literature is keep changing with the time.
In text,a word suggests another word & there is no meaning in word itself. You have to rely on other words.

Thank You.