Since Heidegger Being has refered to Manifestation. What 'is' _is_ what manifests to us, or what makes itself present around and before us.
Thus, Being has depth beyond the abstraction that covers everything. Being is, in fact, the manifestation of everything that manifests. As such it is a dynamic all embracing aspect of the world we find ourselves in the midst of and engaged in before we realize it.
This identification of Being with manifestation owes a lot to Husserl's Phenomenology that distinguished between immanent and transcendent realms bracketing the latter. The transcendent is all the things that we do not know or observe directly in the experience of our consciousness. The immanent is all the things we experience directly in our consciousness. Phenomenology focuses on and describes the Immanent. What is transcendent is the conceptual aspect of Being. The immanent is the manifestation aspect of Being. This distinction gives rise directly to the Kinds of Being.
Being has may interpretations. Heidegger speaks in THE END OF PHILOSOPHY of the different phases of the history of Being. In each phase Being had a different interpretation.
Heidegger also points out that Being is the most forgotten concept. We forget about manifestation because we are completely immersed in it like fish in water. We forget about the importance of the concept of Being because it doesn't seem to have anything special to tell us about anything it is attached to.
The forgetfullness of Being means that manifestation is always emergeing out of and merging back into Oblivion. Oblivion is the ultimate nadir of groundlessness.
Heidegger also points out the 'ontological difference' between beings and Being itself. Being as a whole that encompasses all beings has characteristics of its own that go beyond those of particular beings we might encounter in the world.
Being encompasses the whole world. That is why we can say that ontology is the science of our process of worlding the world. We project the world as our home though establishing our being in it and by dwelling in it through our being in it and part of it.
There are many little known
modern developlments in the study of
Being. These developments mainly took place in Continental philosophy
and may be summarized under the title fragmentation
of Being.
Heidegger, THE END OF PHILOSOPHY
Vail, ONTOLOGICAL DIFFERENCE