Heidegger's existentialism is primarily concerned with the question of being, or the nature of reality. He argues that traditional metaphysics has failed to adequately address this question, and that a new approach is needed.

Heidegger uses the term 'Dasein' to refer to the being of human beings. Dasein is a unique kind of being that is characterized by its ability to be aware of its own existence and to make choices about its life.

Heidegger uses the term 'thrownness' to refer to the fact that human beings are born into a particular time and place, and that they are shaped by the circumstances of their birth. This does not mean that human beings are determined by their circumstances, but it does mean that they are limited by them.

Heidegger uses the term 'care' to refer to the concern that human beings have for their own well-being, for others, and for the world. Care is a fundamental aspect of human existence, and it is what motivates us to act in the world.

Heidegger uses the term 'authenticity' to refer to the state of being true to oneself. This means being aware of one's own existence, one's own possibilities, and one's own limitations. It also means being willing to accept responsibility for one's own life.

Heidegger uses the term 'inauthenticity' to refer to the state of being false to oneself. This means being unaware of one's own existence, one's own possibilities, and one's own limitations. It also means being unwilling to accept responsibility for one's own life.

Heidegger uses the term 'being-in-the-world' to refer to the fact that human beings are always in relation to the world. This means that we are shaped by the world, that we are responsible for the world, and that we are always interacting with the world.

Heidegger uses the term 'temporality' to refer to the fact that human beings are always in time. This means that we are shaped by time, that we are responsible for time, and that we are always interacting with time.

Heidegger uses the term 'historicity' to refer to the fact that human beings are always in history. This means that we are shaped by history, that we are responsible for history, and that we are always interacting with history.

Heidegger uses the term 'finitude' to refer to the fact that human beings are mortal, limited, and imperfect. This does not mean that human beings are nothing, but it does mean that we are not everything.

Heidegger uses the term 'transcendence' to refer to the ability of human beings to go beyond themselves, to create new possibilities, and to choose their own destiny. Transcendence is what makes human beings unique among all other creatures.

Heidegger uses the term 'Being-towards-death' to refer to the fact that human beings are always aware of their own mortality. This awareness is what gives human life its meaning and urgency.

Heidegger uses the term 'resoluteness' to refer to the ability of human beings to face their own mortality, to accept their own finitude, and to choose their own destiny. Resoluteness is what allows human beings to live authentic lives.

Heidegger uses the term 'thrown projection' to refer to the fact that human beings are always projecting themselves into the future, creating new possibilities for themselves, and trying to control their own destiny. This is what gives human life its meaning and purpose.

Heidegger uses the term 'care-structure of Dasein' to refer to the fact that human beings are always concerned about their own well-being, the well-being of others, and the well-being of the world. This is what gives human life its meaning and purpose.