Karl Marx believed class was based on a person's position relative to capital (or the means of production). Marx identified two classes: the capitalist class and the labor class. Capitalists were people who owned the means of production, such as land and factories. Laborers were those who worked for capitalists and produced goods. Marx called the capitalist class the bourgeoisie. He called the labor class the proletariat.
Weber defined class in more complex terms. He defined class as a person's access to three resources: property, status, and power. Weber acknowledges that a person's access to property (capital) was indeed one aspect of a person's social class. However, he believed that other factors related to social standing also influenced class. A person's class is related to how much influence they have in their community, the network of relationships they have, the prestige of their family, etc.