All content records must follow the workflow defined by their content type. A workflow is a series of pre-defined steps along actions available on each step and users who are permissioned to perform them.
Workflows are fully configurable by the Content Settings Administrator and can have any number of steps. A sample workflow is shown below.
In this case, the Marketing Review step would have been restricted to the Marketing user group.
The user that creates the content is considered the Owner and has elevated privileges, similar to a content administrator but on content records where they have ownership rights only. The content Owner can be changed at any time by a Content Administrator.
While in draft or under review (unpublished) states, a content record must always be assigned to a user, this is displayed in the Assigned To field. This is important for tracking and accountability. Content assignment can be changed at any time by the Owner, Current Assigned To user, or a Content Administrator by promoting the content record to another user or reassigning the step to someone else.
The defined workflow dictates what steps are optional vs. required and in what step the content can be published. Typically, publishing would would be the last step but an administrator can give publishing rights to users earlier thereby making subsequent steps optional.
Once published, the content record is locked and typically cannot be edited until a review is initiated. One exception to this is the Quick Edit function which can be granted to certain users to edit content outside of the workflow, typically for minor things like fixing typos. You will know if you have this permission enabled if you see the Save button enabled on the Content Details page of a published content record.