The first zemskiy sobor was held by Ivan the Terrible in 1549. During his reign he held a number of such gatherings and they became a common tool used to enact major pieces of legislation or to decide controversial issues. They usually consisted of nobles and church leaders, but also would sometimes contain representatives of the townspeople.
Under Ivan the sobor had no real power. They were primarily a tool used to rubberstamp decisions that Ivan had already made.
The council continued in this very subservient fashion until the Time of Troubles. When the Riuirikid Dynasty died out in 1598 it was a sobor that appointed Boris Gudunov as the next Czar. The council also selected Michael Romanov to take the throne in 1613.
Once the Romanovs were firmly in power, however, the council lost its power. It also never developed into anything resembling a parliament, unlike royal councils in western Europe.