Originally called Red Army Day the holiday marks the date in 1918 of the first mass draft into the Red Army. In 1919, 17 February fell on a Monday, so it was decided to move the holiday to the nearest Sunday – 23 February.
In 1949, it was renamed Soviet Army and Navy Day. After the fall of the Soviet Union in 1991, the holiday was given its current name in 2002 by Russian President Vladimir Putin, who also decreed it a state holiday (in Russia).
Officially the holiday celebrates people who are serving or have served in the Russian Armed Forces (both men and women), but unofficially it had become a celebration of men as a whole as a counterpart of International Women’s Day on March 8.
The holiday is celebrated with parades and processions in honor of veterans, and women give small gifts to men in their lives, especially husbands (or boyfriends, fiances), fathers, sons and brothers.
Summarized from Wikipedia.
This photograph is the ALEXANDROVSKY GARDEN, MOSCOW. 2008 Wreath-laying ceremony at the Tomb of the Unknown Soldier. It was provided by the President of the Russian Federation website. www.kremlin.ru.