Forms refer to the physical interface users interact with in the Web Application. Forms are created by designers and linked to tasks of a process. System based processes are usually automated and are not linked to forms. An example of a system task is the Scheduler; it will trigger a certain process when the set time has been reached. However, human-based processes require human input in order to advance the workflow.
The image below shows an example of how a human based process is linked to forms. In this example, submitting the form in the first step will trigger the second step.