Since we are studying countries that have been all of these things, we need to be a little more precise in how we use the terms socialism, communism, and totalitarianism.
First, none of these terms refer to social democracy. Social democracies are democracies. They hold free and fair elections. Many social democracies have high levels of state ownership in the economy (in Sweden, state-owned enterprises account for around one-third of the GDP), but they are more generally characterized by large state bureaucracies, high tax rates, and high levels of public spending on social services. You can argue the merits of this type of system, but it’s not even socialism as we think of it today.
The Marxist View
Second, I should mention what communists thought the difference was. According to Marx, socialism was a necessary but temporary step on a country’s path toward communism. Essentially you can have individual ownership of property under socialism (although the state still owns the means of industrial production). And socialists favored gradual reform, rather than the violent revolution required to bring about full communism.
Two dimensions: state ownership and authoritarianism
What do we actually mean by socialism and communism today? I would argue they share two main characteristics: state ownership of the economy and authoritarian politics, but also differ along these two dimensions. Socialist states have some private ownership and enterprise and are electoral authoritarian. That means that they hold multiparty elections, but manipulate them so that the same person or party wins every time. A good example of a socialist state is Venezuela, which began nationalizing its economy and rigging its elections under Chavez and continues today.
Communist states have little if any private enterprise, but are more clearly defined by their politics. They are single party states, where even if they hold some elections, only allow members of one party to run. Communist states are run by communist parties. The best example of a communist state today is probably North Korea, although even that is a bit off due to the hereditary transfer of power there, which is not how communist parties are “supposed” to work.
So technically, there are five communist countries today – China, North Korea, Vietnam, Laos, and Cuba — these are countries run by communist parties that have never held multiparty elections. But on the economic front, most countries have abandoned the communist model to one degree or another. China is the best example. They don’t even call their economic system socialist, but “state capitalism.” The state is still heavily involved in the economy – of the 110 biggest companies in China, only 15% are privately owned – but according to a 2019 study by the World Economic Forum, the private sector accounts for about 60% of China’s GDP and two-thirds of its growth.
Totalitarianism is essentially about state control over every aspect of its citizens’ lives. It has a strong cultural and performative component designed to control how citizens think. By performative, I mean forced participation in public rituals (like parades or demonstrations) designed to make everyone complicit in the regime in one way or another – and to make it difficult to tell who might actually disagree with the leader. They also involve repression on a mass scale – the kind that kills tens of millions of people. So Stalinism, Naziism, and Maoism are all textbook examples of totalitarianism.
So is Russia today a totalitarian state? There are a few aspects of it that fit. Putin does have a bit of a cult of personality and the manipulation of news through state owned media does shape public opinion. But repression and the public performance of support for the regime do not take place even close to the extent it does under totalitarianism. I say this not to excuse Putin or say the repression that exists isn’t that bad, but because blurring the meaning of words is one of things that actually takes place under totalitarianism. I recommend you read George Orwell’s essay “Politics and the English language” for an extended discussion of the value of using words with meaning if you are interested.
So when you describe countries like Russia (or even China), I recommend you keep it simple: they are dictatorships.