One proposal for how to think about the term ‘Dasein’ is that it is Heidegger's label for the distinctive mode of Being realized by human beings...
If we look around at beings in general—from particles to planets, ants to apes—it is human beings alone who are able to encounter the question of what it means to be (e.g., in moments of anxiety in which the world can appear meaningless, more on which later).