Tracking field history is an out-of-the-box Salesforce feature to track value changes in a field. You can define up to 20 fields per object to track. Contact Salesforce support if you need to track more fields. For a long text area, rich text area, and multi-select picklist fields, Salesforce does not track the old and new values when the record is updated, but only track a change has occurred for the field. This feature is simple but powerful for auditing purposes.

Salesforce will retain the data history for up to 18 months. If you need to archive for longer periods, contact Salesforce support to acquire the Field Audit Trail feature and define a policy for the time you wish to retain field history tracking. This payable feature will allow you to extend archiving for up to 10 years.

As an administrator, you can enable field history tracking yourself with a few clicks, and select certain important fields to track for both standard and custom objects...