Literally, poststructuralism refers to the theoretical/critical movement that followed structuralism (Influenced by linguistics and anthropology, structuralism posits that the individual is a product of social and cultural systems, and these systems have embedded in them underlying plots, conventions, and rules (structures) that determine meaning and significance.
Deconstruction challenges the logocentric notion of presence that Western society privileges. Language's meaning is not secured and determined by a presence outside of language (e.g., objects, persons, social and cultural structures). Rather than a transparent medium that reflects meaning clearly, language is an effect that only partially, if at all, reflects "reality" or knowledge about the world. Gaps between what words represent and references in the real word create uncertainty and doubt. Meaning and truth are not impossible to know, but very difficult to determine and require careful reading and thinking at the level of language. Meaning resides within the play of differences between words and the concepts they suggest, within the linguistic system of the text--not outside of it.
For our reading of Ode to West Wind, as an example, the poem is a play of differences in meaning among phrases like "scatter," "unextinguished," ashes and sparks." Also, do we read the last two lines as a rhetorical question or a literal question? How do we understand the wind as both helpful and uncontrollable? As preserver and destroyer? Does the speaker represent a human presence outside of language that guarantees meaning? Or is speech, like writing, subject to misinterpretation and miscommunication? The poem's language itself invites these questions, and the idea of a presence in the poem--Shelley's intention and meaning??--does not resolve them.