Field-level locking locks only the fields modified by an administrator on a first-come, first-served basis. For example, Joe opens the Edit Site widget and changes the Site Category field. At this point, Brightspot locks the field in favor of Joe. When Alice opens the Edit Site widget, she sees a message indicating Joe made a change to the field but has not yet saved it.
When Joe saves the site settings, Brightspot releases the field lock, and Alice can then edit the field herself.