The eagle has been used in symbolism since ancient times, due to its nature as a powerful animal. There are many theories about why the eagle has two heads, and in some civilisations, it was seen as a sign dominance, or control of both the East and the West.
One of the most common interpretations of the two-headed eagle, is of a mythical creature representing Power and Protection. As the official Russian emblem, such a meaning would be highly appropriate in its role as a symbol of nationalistic pride and unity.