After the Tsars and the whole royalist regime was defeated in a very bloody exercise, there came to be two sources of power. It was Lenin who collared the term "dual power" although not the first to use it. It had been so long in Russia that there had been an empire that losing it left an unstable situation.
So political power in Russia was divided between the Russian Provisional Government and the Petrograd Soviet. Ultimately, the soviet understood and carried out the reforms required by the ordinary people better than the provisional governemnt, who more represented the propertied classes.
Hence that government was ousted after a period of shared administrative authority over the country.