Know The Adwords Change History Tool.
What is the Google Adwords Change History Tool ?
The Change History tool lets you see what changes have been made to your account settings/campaign settings.
The tool also shows much mode details than this. It shows who (what login id) did the changes and when they were made.
Thsi tool is used for troubleshooting your google adwords account. For example say you made some changes and things started working great (more conversions/ or high CTR) then you can analyse when the conversions /CTR increased and what changes were been made to the account by looking at the Change History.
The change history tool can be accessed at..
(From Top main menu)Tools & Analysis -> Change History
You can filter the reports by