Meaning of "Being"

"For manifestly you have long been aware of what you mean when you use the expression 'being.' We, however, who used to think we understood it, have now become perplexed."

- Plato's Sopist, Translated by Heidegger in Being and Time

I am convinced that an state of perplexity is probably the most authentic state one can have in relation to the question of "Being." If anyone tells you that they've got it figured out, run away! The question of Being, of pondering what exactly it is to "be" is probably the single most important impetus for our greatest, deepest, and most mystical thoughts and experiences.