Unity Collaborate constantly monitors the changes team members make to your Project. When a team member saves changes to a Scene or Prefab on their local machine, Collaborate notifies you that the Asset has been changed by displaying an In-Progress badge on the Asset.
To view who is working on the Scene or Prefab, hover over the badge.
 
For Scenes, the In-Progress badge is visible in two locations in the Unity Editor:
On the file icon in the Project browser.
 
In the Hierarchy window.
 
For Prefabs, the In-Progress badge is also visible in two locations in the Unity Editor:
On the file icon in the Project browser.
 
In the Inspector window.
 
When a team member publishes their changes, Unity removes the icon and counter.