Actions, used for workflows, can be configured to allow a user to add metadata to preset fields. This way, the metadata entered by the user is applied to all the assets in the selection.
The system administrator may have configured actions that allow users to edit the metadata of the assets they're processing in the action. Both the source asset and the destination asset can be updated. When a user runs such an action a separate window will display and allow the user to edit the content of the fields defined in the action.
Certain fields may have a taxonomy associated with them, in which case the taxonomy will pop up and allow the user to choose content from the taxonomy.
Learn more about selecting assets and processing them with Actions.