Copied from someplace:
Existentialism is a movement in philosophy and literature that emphasizes individual existence, freedom and choice. It began in the mid-to-late 19th Century, but reached its peak in mid-20th Century France. It is based on the view that humans define their own meaning in life, and try to make rational decisions despite existing in an irrational universe. It focuses on the question of human existence, and the feeling that there is no purpose or explanation at the core of existence. It holds that, as there is no God or any other transcendent force, the only way to counter this nothingness (and hence to find meaning in life) is by embracing existence.
Thus, Existentialism believes that individuals are entirely free and must take personal responsibility for themselves (although with this responsibility comes angst, a profound anguish or dread), and emphasizes action, freedom and decision as fundamental in rising above the essentially absurd condition of humanity (which is characterized by suffering and inevitable death).
Turkeys can not fly with the eagles. Sad fact, many of us are born turkeys. There is no evidence that the turkeys and eagles are the same species. We turkeys should be happy as turkeys, and not try to be eagles. Do the eagles become phoenix's when they fly into the sun?
But existential philosophy is so much more, and fits a magpie philosophy of life. It is based on the assumption that our most valuable asset is life, and we are individuals who make our own decisions. Can anyone rationally dispute that?
Existentialism leads to a form of ethics and a form of moral behavior, both derived rationally from the foundation of our life being the most valuable thing to we individual people, and with little more beyond derived virtues, we arrive at a set of ethics that rival Buddhism, the Stoics, the Veda, and surpass christian and muslim dictates. There is no need for faith and religion, no need for a god concept, no need for all those dubious beliefs. Life is good.