According to Marx, there are two classes in capitalism. They are the bourgeoisie and the proletariat. The bourgeoisie take advantage of the proletariat and control the means of production. The proletariat class has more people than the bourgeoisie but do not own the means of production. The proletariat are usually workers.
According to Marxism, many members of the proletariat class have false consciousness. That means they usually think about themselves and are not aware of the class struggle going on in society or how the proletariat is being hurt by the bourgeoisie. An example of false consciousness would be the idea of the American Dream.
When enough members of the proletariat have class consciousness, they will be able to unite and overthrow the capitalist system.