Answer:
The two phases were the February Revolution of 1917 and the October (or Bolshevik) Revolution of 1917.
The February Revolution resulted in the abdication of Tsar Nicholas II and the installation of the Provisional Government (PG). The PG was to operate the government until such time as a Constituent Assembly could be elected, convene and put together a constitutional democratic permanent government.
The October Revolution occurred on October 25, 1917 (Julian calendar date) and resulted in the military overthrow of the PG by Vladimir Lenin and his Bolshevik Party followers.
The Russian Revolution was complete except for the fact that the Bolshevik grab for power was not fully supported by all of the country and the Russian Civil War broke out. By 1920, the Bolsheviks, now called Communists, had overcome the opposing side in the Civil War and became the sole ruling authority in the country.