Tasks are the key components of a workflow. It allows workflows to interact with users using human tasks or modify the data in the workflow using system tasks to provide an outcome for a business process. In a Process App, tasks are further classified into:

Approval Task – It allows you to perform an approval action. For more information, click here.
Form Task – A task where a digital form is sent to the recipient to gather necessary inputs. For more information, click here.
Script Task – It allows you to add or modify the data to use during the execution of a flow. For more information, click here.