It depends on what you mean by a “communist nation.” From a Marxist perspective, communism proper is a mode of production, a stage in the development of human society that comes after socialism. Socialism according to Marxist theory is the transitional stage between capitalism and communism, or what is some these days refer to as “full communism.” Communism in the strict Marxist sense of the term describes a post-scarcity, classless, stateless, moneyless society completely free of exploitation, oppression and coercion. It implies a development of technology and productive capacity (the means of production) to such a high degree that there is a sort of hyper-abundance and compulsory labor is unnecessary. The path from our present state of affairs to that far off ideal is through socialism, which Marx saw as the most efficient and effective way to continue to develop the means of production toward that end.

Now, if you’re talking about a “communist nation” like the Soviet Union or the old Eastern bloc states, it’s an entirety different animal. After the Bolshevik Revolution in Russia in 1917, those in the worldwide socialist movement who supported the Bolsheviks either left or were expelled from the existing socialist parties. They formed new parties that they called “communist” parties to distinguish themselves from the older socialist parties that had given up on the idea of revolution and wanted to establish socialism gradually through electoral reform. The term communist and communism took on a new meaning, describing these new parties, their supporters and the Soviet Union itself. The Soviet Union was however, a socialist country according to Marxist theory, because it was in the stage of development between capitalism and full communism. That’s why it called itself the Union of Soviet Socialist Republics (USSR). Since the Bolshevik Revolution, “communist” had been used interchangeably with socialist when it refers to socialists who advocate a revolution to overthrow capitalism rather than reform.

So now that we have that clears up, we can get to your question.

Soviet style economics were based on state ownership of the means of production and a planned economy. In this case the state constitutes the “collective” that Marx talked about. Instead of Market-driven production motivated by a desire for profits, the Soviet Union and others came up with plans for what to produce and how much based on what they thought would bring the most benefit to people and ensure that everyone’s needs were met as much as possible. This involved a very direct sort of control by the state over production on all (or nearly all) levels. All production, whether it was steel, or coal or wheat or toilet paper was conducted according to the state’s plan with the ultimate goal being to provide for everyone’s needs.

Fascism is an inherently self-contradictory, incoherent and inconsistent sort of system, both in theory and in practice. Because of that it’s difficult to pin down what precisely constitutes a fascist system. There is much debate on the precise definition of fascism and each of the historical fascist states were a bit different from each other and a bit different themselves at different times.

When considering fascist economies, there is one consistent factor that seems to host true and that is the complete subordination of economic production to the interests and needs of the state. There was some production conducted in a more or less capitalist manner, that is to say market-driven and for profit and some under varying degrees of state control. It all depended on what best suited the interests of the state at any given time. As the interests and needs of the state changed, so too did the degree of state control over production. When it was convenient, companies were permitted to continue to produce to generate their own profits and when the state deemed it necessary to its own interests, it would step in and take whatever degree of control it saw fit.

Additionally, there was an element of pageantry to fascist economics. Things were very much for show so that there was a great deal of cutting corners and fudging numbers to make economic output seem far greater than it actually was.

Its also worth noting that fascist countries are ideologically expansionist and war-oriented, and were hence often at war and being on a near permanent war footing had a profound effect on the nature and organization of production.

So the primary difference between the Soviet-style socialist economies and fascist economies was both in their aim and in the role of the state in directing production. Soviet style states had full control over production and organized it according to plans designed to meet the needs of the people (as much as was feasible), while fascist states exercised varying degrees of control over production according to what what in the best interests of the state itself at any given time.