To understand Fascism, one must first understand Capitalism. There are three primary characteristics of Capitalism:
Private ownership of the Means of Production
Commodity Production
Wage Labour
The essence of the Capitalist mode of production is that someone who owns means of production will hire a wage labourer to work in order to produce commodities to sell for profit. Marxists identify economic classes based on this division. Those who own and hire are the Bourgeoisie. Those who do not own and work are the Proletariat. There is far more nuance than just this, but these are the bare essentials. The principal contradiction of Capitalism is that the Bourgeoisie wants to pay the workers as little as possible for as much work as possible, whereas the Proletariat wants to be paid as much as possible for as little work as possible.
Fascism is a form of Capitalist rule in which the Bourgeoisie use open, violent terror against the Proletariat. It is an ideology which emerges as a response to the inevitable crises of capitalism and the rise of socialist movements. It is characterized by all forms of chauvinism (especially racism, occasionally leading to genocide), nationalism, anti-Communism, and the suppression of democratic rights and freedoms. In a Capitalist society, Liberalism and Fascism essentially exist on a spectrum. The degree to which a given society if Fascist directly corresponds to the degree to which the proletariat must be openly oppressed in order to maintain profits for the Bourgeoisie. This why we have the sayings: "Fascism is Capitalism in decay" and "Scratch a Liberal, and a Fascist bleeds"
Capitalism requires infinite growth in a finite system. This inevitably leads to Capitalist Imperialism as well as Fascism, given that infinite growth is not actually possible. When the capitalist economy reaches its limits, the Bourgeoisie are forced to either expand their markets into other territories (Imperialism) or exploit the domestic proletariat to an even greater degree (Fascism). This is why we have the saying: "Fascism is imperialist repression turned inward"
The struggle against fascism is an essential part of the struggle for socialism and the liberation of the working class and oppressed people. However, it is critical to note that simply combatting Fascism alone without also combatting Liberalism is reactionary, because it ignores the fact that Fascism inevitably arises out of Capitalism, so Liberal Anti-Fascism is not really anti-Fascism at all.
Recently, the r/TheDeprogram subreddit was threatened with banning by Reddit admins. I got the go-ahead to mirror the subreddit wiki on lemmygrad in case. I have made a few formatting changes to better suit Markdown formatting and corrected a few typos. Full credit goes to the original authors of the wiki.