From the Wikipedia:
"A planned economy combines public ownership of the means of production with centralised state planning. This model is usually associated with the centralised Soviet-style command economy. In a centrally planned economy, decisions regarding the quantity of goods and services to be produced are planned in advance by a planning agency. This type of economic system was often combined with a single-party political system, and is thus associated with the Communist states of the 20th century.
In the economy of the Soviet Union, state ownership of the means of production was combined with central planning, in relation to which goods and services were to be provided, how they were to be produced, the quantities, and the sale prices. Soviet economic planning was an alternative to allowing the market (supply and demand) to determine prices for producer and consumer goods. The Soviet economy utilized material balance accounting in order to balance the supply of available inputs with output targets, although this never totally replaced financial accounting. Although the Soviet economy was nominally a centrally-planned economy, in practice the plan was formulated on-the-go as information was collected and relayed from enterprises to planning ministries.
Socialist economists and political theorists have criticised the notion that the Soviet-style planned economies were socialist economies. They argue that the Soviet economy was structured upon the accumulation of capital and the extraction of surplus value from the working class by the planning agency in order to reinvest this surplus in new production – or to distribute to managers and senior officials, indicating the Soviet Union (and other Soviet-style economies) were state capitalist economies. Other socialists have focused on the lack of self-management, the existence of financial calculation and a bureaucratic elite based on hierarchical and centralized powers of authority in the Soviet model, leading them to conclude that they were not socialist but either bureaucratic collectivism, state capitalism or deformed workers' states."