What mechanism in Salesforce allows tracking changes to a record field over time?

Field history tracking is the mechanism in Salesforce that allows users to monitor changes made to specified fields on a record. Once field history tracking is enabled for particular fields, Salesforce automatically records when each tracked field is changed, what the previous value was, and who made the change. This historical data can be used to create reports, providing valuable insights into how a record has evolved over time and ensuring an audit trail of significant modifications.

In contrast, audit logs focus on broader system-level activity and do not track individual field changes within a record. Record snapshots capture the state of a record at a specific moment but do not provide ongoing tracking of changes over time. Change sets are utilized for deploying metadata changes from one Salesforce organization to another and do not pertain to tracking record-level changes. Thus, field history tracking stands out as the specific solution designed for monitoring changes to record fields within Salesforce.