There is no doubt that Russia underwent an amazing political transformation in 1917, but the change didn't take place at once.  Most historians agree that there were two separate revolutions in Russia.  The first is commonly referred to as the Russian Revolution and the second the Bolshevik Revolution.

The Russian people called for changes due to a multitude of factors including: lack of food, military incompetence, lack of trust in the leadership, high taxes, lack of freedom, and corruption.  The revolution found success when most of the Tsar's soldiers joined the revolution and forced the Tsar to step down.  A provisional government was put in place putting an end to the revolution.

The Bolshevik, or Communist, Revolution came about as a result of the failures of the provisional government.  People soon saw that it wasn't the answer to their problems and the Bolsheviks, led by V.I. Lenin, gained widespread popularity with the promise of "Peace, Land, and Bread."  Despite some difficulties, the Bolsheviks were able to take control of Russia and instituted a Communist state.