A business process is the flow of information (or documents) by a previously defined route or scheme. A business process scheme can specify one input and one or more output points.
For a business process, it is common to run on a certain object and alter the execution flow depending on the object state. An underlying object is called a document which can be a file (saved in Document Library), an information block element, or a CRM item.
The following system objects are supported as documents: