Time and the laws of Nature

What is time? Why does it "flow" and why are we sure that it flows from past towards future? Why is there such a gigantic distinction between the Past of our world, which we believe to be fixed, and the Future, which we consider undetermined? And this is in spite of the fact that almost all physical laws are time-symmetric! Why does previously undetermined "Future" acquire its steadiness as it passes the moment called "the Present"? Perhaps, these questions are partially answered in the considerations below.