  Entropy concept was introduced by Clausius 160 years ago, and has been
continually enriched, developed and interpreted by the researchers in many
different scientific disciplines ever since. Thermodynamics and other
scientific disciplines face several simple but crucial questions concerning the
entropy concept. Thus, it is frequently possible to notice a misuse of entropy.
Sometimes unbelievable confusion in the literature is summarized by von
Neumann's sentence: "No one knows what entropy really is." Four major questions
stand before thermodynamics. (1) How many kinds of entropy are there? (2) What
is the physical meaning of entropy? (3) Is entropy a subjective or an objective
property? (4) Is entropy in any way related to information? This paper attempts
to describe the roots, the conceptual history of this important concept and to
describe the path of its development and application in different scientific
disciplines. Through this we attempt to give some possible answers to the
questions mentioned above.
