The term "facticity" was originally coined by Martin Heidegger in Being and Time ("Sein und Zeit"). He uses the term in a slightly different sense. Facticity is not synonymous with being, but is fundamentally connected to the being of Dasein. Dasein is always in the world, that is to say, we cannot separate being from "being-in" a world, a situation, a body, even. Facticity is the concrete aspect of Dasein.
Existence cannot be explained as the presence of a transcendental subject which is fundamentally separate from an objective universe. The world of Dasein is an existential structure of its Being.
For more hyphens and untranslatable German words, as well as a modicum of clarity, read some good old Martin.