Martin Heidegger’s texts are among the most difficult in the philosophical literature throughout the world. Paradoxically, despite they are commonly considered as untranslatable, they belong to the most frequently translated twentieth-century philosophical texts. High availability of translations makes the thought of Heidegger still enjoy great interest and result in a number of comments. The constantly growing number of translations of his texts affects shapes of national philosophies and their issues. It is particularly clearly visible in Poland where for a long time the philosophy of Heidegger was available only to the narrow circle of the German-speaking philosophers. The situation has changed significantly since the early nineties, when there rapidly began to appear translations of his major works. However, a different problem occurred – namely the problem of translation. It is nowhere so much invisible as in the case of two basic words: bycie (Being) and byt (being). This text follows various ways of translating and interpreting of Heidegger’s terms, asking about their philosophical relevance and relationship to the established philosophical tradition. Not denying any previous choices, it tries to develop a relevant criterion for understanding the two concepts. In order to do this, it tries to reveal the most important idea of Heidegger’s philosophy.