The Campaign Activity History tab lets you see what changes have been made to your Campaign since it was created.
You can access the Campaign Activity History tab from the Campaign Summary Page, click on Campaign Activity History.
On the Campaign Activity History tab you can search for keywords and use the Activity Selector to filter by dates, filter by API that was used to make the changes. The Columns drop down menu allows you to choose what information you want to see on the page, including viewing the JSON information from the change request.