Class processes are those economic processes involving the production, appropriation, and first distribution of the surplus products (or surplus value) created by direct producers.  The adjective placed in front of class (such as slave, feudal, capitalist, ancient, or communal) is determined by the particular social arrangement by which the fruits of the direct producer's labor are appropriated and distributed.  Although there are many similarities between the various class processes, it is assumed that the differences are consequential and worth fighting over.
The concept of class process is the entry point into social analysis for post-structuralist Marxian theory. The concept of "class" is closely associated with Marxist social critique and analysis.  However, there are significant differences among Marxian theorists over the significance and  proper way to conduct class analysis, and the very definition of class.  Some Marxian theorists have focused on property relationships.  Others have focused on political (power) relationships.  Post-structuralist Marxian theorists, and some other Marxian theorists, have returned to the definition that Marx produced --- class as the appropriation and distribution of surplus labor (in direct labor form, product form, or value form).  Use of the phrase "class process" is linked to the overdeterminist ontology deployed by post-structuralist Marxian theory. 
The worker's total working day
is divisible into two parts.

One part is that in which
he performs the quantum
of labor needed to reproduce
the value of his own
means of subsistence.

The entire remaining part . . .
is surplus labor.

---Marx