What the Bolshevik Revolution did was to destroy the provisional government that had been formed after the overthrow of Tsar Nicholas II. After destroying the provisional government, the Bolsheviks took power, although they had to struggle to hold on to that power during the course of a civil war against "white" Russians who wanted to go back to the old system. When this war ended in 1921, the Bolsheviks were in complete control.
In the bigger picture, what the Bolshevik Revolution did was to bring into power a communist government in Russia. This government, which created a new country called the Soviet Union, was to hold power until the early 1990s.
Overall, then, the Bolshevik Revolution overthrew the more democratic provisional government and set up a communist government that soon became a totalitarian regime.