What is the difference between the “Approve or Reject” and “Approval only” step types?
Approve or Reject
The 'Approve only" option allows the user to only Approve the request. This restricts the process from continuing till the Approver is absolutely happy with contents of the task. If the user required details to be changed, he/she can "Request a change" back to the specific user, to make the required change and approve the task thereafter.