In this essay, the first of the two Einstein's relativity papers of 1905 is discussed. In section 1 a concise overview is given of some circumstances that were a prelude to the paper, as well as of the scientific activity of Einstein's predecessors. It is argued that, contrary to the conclusions they had been forced to draw, the paper offered a completely new perspective of the world. The next three sections contain comments on the contents of the paper: on the relativity principle and its results related both to the new kinematics and electrodynamics. In the last section the author makes a comparison, in very general terms, of the 1905 Einstein theory with the contemporary theory of special relativity.