This is an attempt to meet Venny's request. Very offhand, please note.
Pluralism: the theory that there are not only different but incommensurable universes of discourse, such that communication between universes is impossible. Thus I say X and you say X, but we mean quite different things. I say this is a theory, because we could question whether pluralism is so radical as to prevent any possibility of communication. Wittgenstein himself said: if a lion could talk, we would not be able to understand it. I read this as saying: between human beings, however different we are, we can communicate, because there is something shared, a form of life, a common humanity, at least operatively if not in thought content.
Hermeneutics: earlier this was understood as the art of interpretation. After Heidegger and Gadamer, it is understood not merely as an art of interpretation, but as the very way we are. We are hermeneutical beings, beings that live as interpreters. Now within such a hermeneutical philosophy, one can opt for a radical pluralism of the sort described above, or else for a not so radical pluralism that still makes space for the common ground of a common humanity...
Reception: the idea that meaning is created in the receiving. Thus, for example, there would be no abstract 'meaning' of a work of art; rather, meaning emerges in the reception of that work. And so there would be a multiplicity of meanings. Is this multiplicity radical, so that there is no connection at all between different meanings? There would be different opinions here. A radical postmodern position would probably talk about the 'text' (or work of art) as absorbing the 'world' or 'reality', rather than 'referring' to a world or reality.
Postmodernism: still an umbrella term that covers a wide variety of positions, chiefly those of Lyotard, Derrida, Foucault, Rorty, Vattimo. An ongoing contemporary realization of the shortcomings of modernity beginning from Descartes. E.g. there is no 'enclosed subjectivity' but always being-in-the-world. Reason is not supreme; it has to become aware of its fragile, fractured state. There is no such thing as pure reason; reason is always 'engaged', situated, committed, situated, historical, conditioned, traditioned... There are no meta-narratives or grand narratives, or if there are, they should be recognized as 'constructs'; there are only little narratives. Centres are centres only because of power equations; the margins must be respected, looked at, focussed upon, recognized, given their due. Superficiality and play rather than profundity. No common ground, therefore, but a play of a thousand forces and aspects and dimensions. No 'foundations' for truth. Not even 'truth' in the classical sense of correspondence to reality, but existential truth, truth in the living out, pragmatic truth.