Setup Audit Trail tracks the recent setup changes that you and other admins make. Audit history is especially useful when there are multiple admins.
To view the audit history, from Setup, in the Quick Find box, enter View Setup Audit Trail, then select View Setup Audit Trail. To download your org’s complete setup history for the past 180 days, click Download. After 180 days, setup entity records are deleted.
The history shows the 20 most recent setup changes made to your org (scroll below to download the 6 months' history in an Excel sheet).
The Audit Trail lists the date of the change, who made it, and what the change was. If a delegate such as an admin or customer support representative makes a setup change on behalf of an end user, the Delegate User column shows the delegate’s username. For example, if a user grants login access to an admin and the admin makes a setup change, the admin’s username is listed in the Delegate User column. The user granting access is listed in the User column.
Setup Audit Trail tracks these changes.
For history tracking of fields on an object, please see the following article: Set History Tracking of an Object