In EBS Sandbox related to Server but in Oracle fusion Sandbox is totally different concept.
In Oracle Fusion , We will Use Sandbox to do any kind of Personalizations or Extensions or Page layout changes in Oracle Fusion Web-pages. It means we need to create Sandbox first to make any changes in Oracle Fusion application in terms of Personalizations or Extensions. Then all the changes will be done under this sandbox and this is the important feature of the sandbox that , we can do the changes in the application without impacting the complete application so these changes will only apply under the sandbox and other users of the application will not see these changes until unless you have tested the changes under sandbox and publish this sandbox. Once you will publish the sandbox in fusion then all the changes under the sandbox will be published to all the users in the application.