In March 1917, when the tsar's government collapsed, the members of the Duma set up the Provisional Government, led by Alexander Kerensky.
The Provisional Government never really ruled Russia. Right from the start, it had to share power with the Petrograd Soviet, which had a rule (Order No.1) that its members should only obey the Provisional Government if the Soviet agreed with it. For this reason, March to November 1917 is sometimes called the period of Dual Government in Russia.
Disastrously, the Provisional Government - because it was only a temporary government - did not really carry out any major reforms. All it did was abolish the Okhrana and press censorship, and allow political freedom. This gave the government's opponents - such as Lenin's Bolsheviks - the freedom to attack the government for the problems it was not solving.
The main problem of the Provisional Government was that it tried to continue the war. In June 1917, it organised an attack on Austria. When the attack failed, people began to turn against the government. Instead, they started to follow Lenin whose welcome message was: 'Peace, bread, land'.