Can you explain the principles of existentialism?

UM professor gave us the following principles i do not know how they relate to each Another concern of the presence of the absurdity of the existence of death – without meaning to real life – do not lie to yourself how are existentialism? and if possible, could u give me a definition of existentialism?

Ok, existentialism says that virtually all we know is that we live (any). We have no way of knowing the reason (and no objective justification for believing) that something like a much bigger or organizing principle, no. All we have is what we live, which derives from our existence. This leads to the absurdity of life. With no higher principle of life, life has no objective meaning. We're here, we exist, we die, no action or choice can not change this fundamental reality in any way. All we have is our own subjective experience. A lack of choice or action with a sense of superiority, the only way to justify the progress is in line with what we are. It's true. If we think that act reasons other than our own will, we deceive ourselves and try to live in a dream world does not exist. Anxiety in the presence of death arises because we realize that all we really have is our life. However, we also recognize that death eventually, and this marks the end of our existence. The absolute end troubles us because it is so contrary to life. (For this reason, people do things like religion and beyond to try to put your mind at ease. They use moral religion as a crutch to avoid the harsh reality that we ourselves and there is nothing to prevent us from doing what you choose.)

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