[1] When Leibniz speaks of a possible world, he means a set of compossible, finite things that God could have brought into existence if he were not constrained by the goodness that is part of his nature.
The actual world, on the other hand, is simply that set of finite things that is instantiated by God, because it is greatest in goodness, reality and perfection.
[2] Views on "compossibility" and the closely related best of all possible worlds argument are to be found in On the Ultimate Origination of Things, The Discourse in Metaphysics, On Freedom, and throughout his works.
[1] Alain Badiou borrows this concept in defining philosophy as the creation of a "space of compossibility" for heterogeneous truths.
[citation needed] Gilles Deleuze uses it in Cinema II taking support from Leibniz's explanation of the problem of future contingents.