The flag of Mongolia consists of two vertical red bars and one vertical blue bar.  The symbol on the left hand side of the flag is the Soyombo, the national symbol of Mongolia. 

The Soyombo or Swayambhu in Sanskrit has served as Mongolia’s symbol of independence for many centuries.  The origin of the Soyombo goes back to Zanabazar,  the first Bogd Jebszundamba, who was head of the Buddhist lamasery in Mongolia during the 17th Century.  He invented the Soyombo Script and the current national insignia was the first letter of this script.

Ts. Erdenebat gives this explanation of the meaning of the symbol .

    * The three tongues of flame on the top symbolize the glories of the past, present and future.
    * The sun and moon represents the heavens.   Mongols have long worshipped the blue sky, the sun and the moon.
    * The triangle below symbolizes a family, a father, mother and a child: the hearth of a nation.
    * The quadrangle under the triangle symbolizes the four cardinal points of the compass.
    * The pair of fish, depicted in the center, symbolizes growth and prosperity for fish grow very fast.
    * The lower triangle represents heaven, earth and water: the realms of all living creatures.
    * The two vertical quadrangles, bordering  both sides, are the golden pillars of the State.